You need to keep in mind that the press freedom ratings is not a measure of freedom of speech, but freedom of the press, and the US is still ranked as "fairly good".

Specifically, the index describes itself:

What does it measure?

 

The Index ranks 180 countries and regions according to the level of freedom available to journalists. It is a snapshot of the media freedom situation based on an evaluation of pluralism, independence of the media, quality of legislative framework and safety of journalists in each country and region. It does not rank public policies even if governments obviously have a major impact on their country’s ranking.

They also provide more detail about their methodology and the questionnaire used to create the index is available online.

I was unable to find a full report, but in a short analysis, the index specifically mentions Trumps hostility to the media.

They go into a bit more depth about this in a press release for the 2017 data:

In 2017, the 45th President of the United States helped sink the country to 45th place by labeling the press an “enemy of the American people” in a series of verbal attacks toward journalists, attempts to block White House access to multiple media outlets, routine use of the term “fake news” in retaliation for critical reporting, and calling for media outlets’ broadcasting licenses to be revoked. President Trump has routinely singled out news outlets and individual journalists for their coverage of him, and retweeted several violent memes targeting CNN.

 

The violent anti-press rhetoric from the White House has been coupled with an increase in the number of press freedom violations at the local level as journalists run the risk of arrest for covering protests or simply attempting to ask public officials questions. Reporters have even been subject to physical assault while on the job.

 

However, the Trump effect has only served to amplify the disappointing press freedom climate that predated his presidency. Whistleblowers face prosecution under the Espionage Act if they leak information of public interest to the press, while there is still no federal “shield law” guaranteeing reporters’ right to protect their sources. Journalists and their devices continue to be searched at the US border, while some foreign journalists are still denied entry into the US after covering sensitive topics like Colombia’s FARC or Kurdistan.

You need to keep in mind that the press freedom ratings is not a measure of freedom of speech, but freedom of the press, and the US is still ranked as "fairly good".

Specifically, the index describes itself:

What does it measure?

The Index ranks 180 countries and regions according to the level of freedom available to journalists. It is a snapshot of the media freedom situation based on an evaluation of pluralism, independence of the media, quality of legislative framework and safety of journalists in each country and region. It does not rank public policies even if governments obviously have a major impact on their country’s ranking.

They also provide more detail about their methodology and the questionnaire used to create the index is available online.

I was unable to find a full report, but in a short analysis, the index specifically mentions Trumps hostility to the media.

They go into a bit more depth about this in a press release for the 2017 data:

In 2017, the 45th President of the United States helped sink the country to 45th place by labeling the press an “enemy of the American people” in a series of verbal attacks toward journalists, attempts to block White House access to multiple media outlets, routine use of the term “fake news” in retaliation for critical reporting, and calling for media outlets’ broadcasting licenses to be revoked. President Trump has routinely singled out news outlets and individual journalists for their coverage of him, and retweeted several violent memes targeting CNN.

The violent anti-press rhetoric from the White House has been coupled with an increase in the number of press freedom violations at the local level as journalists run the risk of arrest for covering protests or simply attempting to ask public officials questions. Reporters have even been subject to physical assault while on the job.

However, the Trump effect has only served to amplify the disappointing press freedom climate that predated his presidency. Whistleblowers face prosecution under the Espionage Act if they leak information of public interest to the press, while there is still no federal “shield law” guaranteeing reporters’ right to protect their sources. Journalists and their devices continue to be searched at the US border, while some foreign journalists are still denied entry into the US after covering sensitive topics like Colombia’s FARC or Kurdistan.