I read several articles on why Russia is interested in Ukraine. But not much found on why USA is going after it. Appreciate if someone can explain this to me.
The US's only interest in Ukraine is to keep Russia out of Ukraine. The US maintains a containment strategy on Russia, meaning that it tries to keep Russia from expanding and becoming a powerful empire and military adversary. It does not want Russia to expand into its former USSR territories. NATO exists for this express purpose to defend nations against the aggressions of Russia.
The US's allies are interested in Ukraine because the gas pipeline goes through it and Russia can turn off the gas to Europe and increase prices. The US cares for its allies as well and doesn't want this to happen either, of course. The US along with its allies are trying many ways to try to wrestle monopolistic control away from Russia over Europe's gas prices and Russia is trying to further monopolize fuel internationally through the pipeline. The US gets it fuel from other sources, but it is still involved in this international manuveuring.
For the second paragraph, see:
- There are several US/NATO allies which border Ukraine - To maintain credibility in the organization the US has to do more than simply show concern that Russia is attempting to coerce a sovereign nation into acquiescing to its territorial demands.
- The US was instrumental in Ukraine relinquishing its nuclear weapons (which were left on its soil after the collapse of the Soviet Union) by ensuring that the country became part of its "Partnership for Peace." A strong case can be made that Russia would not have invaded the Crimea had these weapons remained in Ukrainian control.
- Western Europe is essentially militarily defenseless against Russia - When NATO was in force, the threat of military action was enough to deter Russia from expanding into Western Europe. With most US troops now at home and NATO essentially a political and not a military organization, it is incumbent upon the US to maintain the integrity of Western Europe.
- Several NATO members directly border Russia - If Russia is allowed to succeed in Ukraine, then later issues against NATO members may be attempted by the country if the US is not seen as responding forcefully enough. After all, an attack against a NATO member is an attack against the collective group.
The dual geopolitical events of 1991, the Persian Gulf War, and the collapse of the Soviet Union, established the United States as the world's sole, unchallenged superpower.
The United States would like to see a strong and independent Ukraine, preferably allied to NATO to prevent a resurgence of Soviet power. The Russians see a friendly Ukraine as an armored belt against western aggression. And China wants to see a strong Russia, hence a subservient Ukraine as an embarrassment to the United States. That is, until Russia starts interfering with China's interests at some point.
Beside of all aspects listed in existing answers, I would like to draw your attention to yet another two reasons, what's the United State's interest in Ukraine, which seem to be missing in other answers.
U.S.' interest in Ukraine rather has indirect nature, but it is caused by a very powerful factor, striving to keep post-Yalta security order. Shortly,
- Post-Yalta world introduced a "bi-polar world", U.S. was one of the poles;
- Post-Yalta world has also assumed no further annexations in Europe;
- USSR collapsed, and it is "biggest disaster" for today's Russia;
- Russia wants to revive the USSR;
- By their own will, no nation would want to be in the newly-created USSR;
- So Russia wants to review the post-Yalta security order and by using military forces, make other states into the newly-created USSR;
- Which is unacceptable for U.S. Here's the interest.
- Ukraine has surrendered its nuclear arsenal (3rd in the world by size);
- In exchange, other states, including U.S. have promised to respect Ukraine's independence and sovereignty within its existing borders; it was not stated directly, but assumed that nuclear countries will defend Ukraine in case of external aggression;
- Other countries today have built nuclear weapons (or are close to) — consider Iran, Libya, Pakistan, Egypt, Argentina, Brazil, and South Korea;
- U.S. consistently provide with measures of nuclear containment, they are negotiating with these countries to surrender those weapons, in exchange or respecting their borders and helping in case of external invasion;
- If U.S. does not keep their word given to Ukraine, all further negotiations on nuclear containment make no sense. Countries will need to re-start their nuclear programs.
- Which is unacceptable for U.S.
Long answer on Reason 1
After WWII, "post-Yalta world" has been established, including all created after 1945 mechanisms of mutual containment, security, negotiation, and international law. In fact, it became a bi-polar world.
U.S. was one of the poles. The other pole was USSR that collapsed by results of Cold War.
Note, "post-Yalta" world assumed that there will be no annexations in Europe anymore. This agreement was kept:
- After collapse of Soviet Union, the newly formed states were created within borders of ex-Soviet republics;
- Even in Kosovo, Albania has never attempted to annex it, although large part of Kosovo population are native Albanians;
There were only two times after WWII when one country has attempted to annex a part of another:
We all know what the international reaction was. U.S. played the key part in both cases.
Back in 2005:
President Vladimir Putin of Russia has described the break-up of the Soviet Union as the "greatest geopolitical disaster of the last century".
Logically, he sets his primary goal revival of the Soviet Union:
"President Putin has a dream to restore the Soviet Union and every day he goes further and further and God knows where is the final destination," — Ukraine PM.
"Putin’s attempt to recreate the Soviet empire is futile" — Financial Times
Such revival, in theory, can be done in a peaceful manner. If Russia was a powerful state with good economy basis, human freedoms, etc., probably, other nations would like to join such a prosperous state (or unions with this state). But with current pitiable status of Russia it's simply impossible. For instance, according polls, that even the poorest territories in Ukraine (ironically, they are most pro-Russian) did not show sufficient loyalty to Russia.
Hence, the only way how Russia can take other nations to join the newly-created Soviet Union is by force. And the only way to force Ukraine to do that in annexation of Crimea, Easter Ukrainian districts, and so on.
This is unacceptable for the United States.
Nuland: Elections in Ukraine a matter of national security for United States
Long answer on Reason 2
Budapest Memorandum states the following:
- Respect Ukrainian independence and sovereignty within its existing borders.
- Refrain from the threat or use of force against Ukraine.
- Refrain from using economic pressure on Ukraine in order to influence its politics.
- Seek United Nations Security Council action if nuclear weapons are used against Ukraine.
- Refrain from the use of nuclear arms against Ukraine.
- Consult with one another if questions arise regarding these commitments
The United States was one of the guarantors.
Russia broke their word, but (personal opinion) nobody in Ukraine has actually believed the words of Russia.
However, if U.S. breaks its word, all further agreements with countries who have developed nuclear weapons or who are close to it, would be useless. Everyone will suddenly realize that only possession of nuclear weapons can really defend them.
Summarizing all above.
United States are interested in keeping existing security order in Europe. Since Russia is trying to ruin this model in Ukraine, U.S. are trying to resist that.