Why does the main left-wing party in the United States (the Democratic Party) hate being called "socialist", but in France the main left-wing party proudly calls itself "the Socialist Party"?
Because US Democratic party is not left wing, it's just slightly more to the left than extremely right wing Republican party.
This is an important point, one that is worth expanding. The ideology of the Democratic Party is closer to that of European Centre-Right parties like the UK Conservative Party and the German CDU than it is to the European Centre-Left, like the UK Labour Party and the French Parti Socialiste.
In fact, on many issues the UK Conservative Party is to the LEFT of the Democratic Party; think, at random, of gun-control, national health service, and campaign financing.
Others have raised a related hypothetical: with whom would the US parties caucus if they were in the European Parliament? If the Democratic Party linked with the Conservative Party and the CDU in the EPP,where they belong ideologically, then the Republicans would find themselves with the HARD-right nationalsts in the ECR (not the FAR-right extremists in the EFD.) I apologize for the flurry of acronyms; I'm just trying to keep it short.
There are many in the United States who lack a basic understanding of Socialism in even a few of its many forms. The most damning indictment is when a person uses Communism, Nazism, and Socialism as though they are synonyms. It would be lost on them to attempt to explain nuances between Social Democracy and Democratic Socialism.
There are numerous programs in place here in the United States that are clearly Socialist. Most will probably object to something, if only to opine that the program isn't structured properly, but only the most ardent proponents of Objectivism, Minarchism, and Anarcho-capitalism would object to Socialism in all forms.
I've listed but a few programs below.
CDC, FDA, Farm Subsidies, Fire Departments, Infrastructure, Libraries, Medicaid, Medicare, National Weather Service, OSHA, Public Museums, Public Parks, Public Schools, Public Transit, Public Utilities, Public Zoos, Unemployment Insurance, Vaccines
Many parties of all political stripes probably could be chided for a lack of clarity in their names. The two predominate parties in the U.S.--the Democratic Party and the Republican Party--specific two components of our system of government, which is a constitutional republic with democratically elected representatives. It isn't very intuitive to one that the Democratic Party is center left and the Republican Party is center right.
On the matter of parties bearing the name socialist, in France and other European democracies, one could observe the inconsistency over the issue of healthcare. 33 out of 34 OECD nations, most of which are in Europe, have some form of universal or single payer healthcare. This is derided as socialist here in the U.S. The Swiss system bears some resemblance to some aspects of the Affordable Care Act (ACA), aka ObamaCare; however, it is true universal healthcare, unlike ACA here in the U.S.
Mainstream center right parties in European parliaments are in support of their respective universal healthcare systems, but most would eschew the term socialist.
This could be traced back to the Cold War era, when socialism and the USSR was the mortal enemy of the US. Any party nowadays wouldn't want to associate themselves with the old enemy.
Also for most people, 'socialism' strongly recalls in their memory the crimes committed by the various socialist proclaimed regimes around the world.
Other answers have commented on the US side of the question but I am not sure that France's Parti Socialiste “proudly” calls itself socialist. In fact, the prime minister (who presently comes from this party) floated the idea of changing its name less than a month ago.
In any case, most European centre-left parties have kept their traditional name (“Sozialdemokratische Partei Deutschlands”, “Parti Socialiste”…) independently of any ideological changes or their position on a left-right axis. So in Switzerland or Belgium you have a “parti du travail”, which is a small far-left party and a “party socialiste” which is a mainstream centre-left party. In the Netherlands, it's the opposite, the Partij van de Arbeid (“Labour party”) is a mainstream social-democratic party and the Socialistische Partij is a far-left protest party (it used to be a fringe group but recently had some electoral success).
In fact, in many cases, the changes have been so thorough that the name is basically all that's left. Whether you welcome those changes or not, the name really does not matter so much. In France, the Socialist Party has been in power several times, its platform is decidedly moderate, the party big-whigs are all career politicians coming from the same schools than other politicians. The voters know that and nobody would make the mistake of thinking that this party aims at upsetting the current regime in any way (by contrast, when Mitterrand came to power in 1981, the party had some radical proposals, the Soviet Union still existed and some people had a genuine fear of some sort of revolution).
It also seems that the main dividing line between left and right in France is now based on social issues like gay marriage and not so much on economic policy. Both main parties basically manage the economy in a centrist and EU-agreeable way while trying to please special interests or not to annoy their main constituencies too much. Recently, right-wing politicians seem loath to debate the economy in detail because they don't really have any concrete plan on how to do things differently than the current nominally “socialist” government.
Incidentally, the proposal to change the name was met with a backlash. The left-wing of the party had to swallow a lot but they would not contemplate that.
In early 20th century America, communism was viewed as a threat to the "American way of life." Socialism was viewed as simply a variation of communism.
At the time, there were Communist and Socialist Parties. Many of the members of these groups were what many Americans viewed as undesirables (i.e. immigrants, Jews and the poor). Many Americans began equating Socialism (in it's many forms) with Undesirables. A good example is the case of Sacco and Vanzetti. Two Italian immigrants accused of being members of a group who robbed the pay role of a shoe factory and killed several guards. Even though the case offered no evidence that they were involved and the defense had witnesses that they were far removed from the crime scene at the time they were both convicted simply because they were members of the American Socialist Party and handed out flyers.
This anti-socialist propaganda came to a head during the McCarthy hearings of 1954. Although the hearings were directed against the American Communist Party, Americans tended to group all the differing ideologies into a generality. To be socialist/communist became equivalent to being "anti-American."
Today, if a politician mentions the word Socialism in a positive light, they run a high risk of losing their next election or being thrown out of office.
While perhaps diminished largely in practice since the 1930s, the notion of individual freedom has played an enormous role in the American psyche ever since the American Revolution. This tradition in American history can not be easily overstated. Anything that they view as autocratic in nature will immediately be met with suspicion by most Americans. Since socialism necessarily involves less personal freedom, it is immediately met with distrust. This distrust for socialism increased dramatically after WWII as the U.S. entered the Cold War against Communism in general and fought Communism in actual wars in Korea and Vietnam. Thus, the word 'socialism' gets associated with two things that are viewed very negatively in the U.S.: lack of individual freedom and Communism.
Because the Democratic Party is still in denial about being a left-wing party.
At its peaks (in the 1930s and mid-1960s), the Democratic Party was a majority party -- and its core was the established political order of the South. At the same times that FDR was implementing the "New Deal" and LBJ was proposing the "Great Society", the Democratic Party was still a party of traditional values (including the flag, motherhood, and apple pie).
Today, there is a major class difference between the Democratic Party and the Republican Party. But the class divide is about attitudes toward marriage and "affordable family formation", rather than income sources.
American public opinion has different focus than French. In France so called 'French Revolutions' is still being celebrated, even though number of atrocities were committed, including the first modern genocide (war in Vandee). French were always looking at the crimes committed by socialists in Eastern Europe from Sartre'a perspective. According to him, all crimes were justified, because socialists were fighting for a better world.
It seems that people in Europe are not able to associate the failures of India and China economies prior to 1990s with their socialists politics. They would even deny that socialists ever ruled India (vide Nehruvian socialism).
In America socialism is more closely associated with its true meaning (means of production owned or control by the whole society), while in Europe it is associated with social security.
I will keep it short since most people answered the semantics.
Just because they are both considered "left-wing" parties, doesn't mean they aren't different. By assuming they both would be the same, would be to assume that both are the same in every way. Even by saying left/right wing would indicate that there are only 2 (main) parties and must think a certain way.
It's just a mix of cultures, histories, and stigma.
Because the name does not matter. In Cyprus and in most of Europe the socialist, communist and general "left" parties are only using the name Socialists to differentiate themselves for voters. Their views as a party have nothing to do with economic policy of a socialist anymore because their main purpose and mindset is greed (just like all human beings that get sucked in the system of politics). We have left parties, right parties and center parties and they are all the same, 90% similar views about economic policy (which in theory should be one of their most basic differences) and everything else is the same.
So more or less the fact that French or any other country "left parties" like to be called socialists has nothing to do with them being socialists but more to do with wanting to sound like socialists.
In the US the terms communist, nazist and socialist are considered synonyms (not to each other but) to the terms dictator and enemy of the country) . That's how most Americans view it. So if a party would be called one of those three then automatically they would lose their vote count because of some people's understanding, while in Europe using those terms might increase your votes.
I mean if you think about it, Hitler's political party was socialist in the name. I mean by Nazi name it actually meant National Socialist German Workers' Party. But can you imagine a socialist and a Nazi agreeing on anything?
The US Democrat Party certainly is a socialist party which believes in big government, centralized power and an expanded welfare state. It began moving to the left around the middle '60's and these days is influenced by many radical leftist organisations (Soros, MoveOn, Media Matters, Acorn, Communist Party USA, ACLU, Feminist movement, Greens....etc).
However it doesn't like being called a socialist party because Americans have traditionally seen the US as a center right nation. Therefore the Democrats like to pretend that they are moderates while claiming to stand for middle class and working class Americans. Europeans on the other hand have historically embraced socialism more readily than Americans therefore the center-left parties in Europe have no problem using the 'socialist tag'.
I think it was Oscar Wilde that said ‘We have everything in common with Americans except language.’ So perhaps it’s not surprising that the terms mean very different things in Europe and in the US, given their vastly different experiences.
Socialism in the UK, at least in today’s UK after a generation of neo-liberalism is seen as eccentric rather than dangerous or respectable. It was once a dangerous idea, like all new ideas are. But it was also respectable because many had seen the inequities of capitalism, in what was the crucible of capitalism.
Chomsky points out in his books that the US public, by and large, are largely to the left of the elites. This he said explained the unexpected success of Bernie Sanders in the presidential race a couple of years ago. It simply, that with the media being in the hands of the elites, that these views don’t get a proper hearing. A people need to hear itself speaking to learn what it is that they truly thinks.
The question then becomes - why is the word Socialism such a dirty word for the elites? Surely this explains itself: the USA was founded as a business, and though it is said to be a country without an aristocracy, I would beg to differ. It is a country with an aristocracy, an aristocracy of enormous wealth, power, privilege and prestige - and mostly white. The USA is, in essence, an oligarchy (which helps explains Chomskys observation on what he calls their Propaganda Model). Moreover, one should not forget the Cold War when the USA faced off USSR for forty years and in that elemental opposition, socialism was put into opposition with the freedom, democracy and the free-market. It’s no surprise then, that the word socialism became a dirty word amongst the USA elites.
The Democratic Party generally does not like to be described as socialist because they do not generally favor state ownership of the means of production.
Until recently, the term "socialist" in the United States was understood to typically be applied to individuals or groups whose stated goals or beliefs included state ownership of the means of production. Examples of such groups would include Communist parties that ran various states comprising the Soviet Union and associated second-world countries. The Democratic Party was often opposed to such political movements, especially during the earlier parts of the Cold War.
Today in America, the term "socialist" is poorly understood and has multiple meanings associated with it, in part because individuals on the right and the left use it to mean things other than state ownership of the means of production. It is increasingly being used to refer to the public provision of goods or services. The public provision of goods and services is part of what all governments do, and does not require or imply public ownership of the means of production.
The Democratic Party is generally in favor of expanding the public provision of goods and services. It is not generally in favor of state ownership of the means of production.