Of the ten most populous countries in the world, only China (2.114) and Indonesia (1.783) have lower peace indexes than the United States (2.337). Of the next ten, only four have lower indexes. In other words, two thirds of the twenty most populous countries in the world (of which the U.S. is third) are more violent than the United STates. Unless by the "rest of the world" we're going to ignore most of the people?
[0]: https://worldpopulationreview.com/country-rankings/most-viol...
To say that the US has a worse peace index than the rest of the countries in the world is still hyperbole, but it's not so far off the truth.
The US has the 129th best peace index of 163 countries, right after Egypt, Zimbabwe, and Azerbaijan.
It does not imply necessary that America is worst country in the world overall.