As humans we often take assertions at face value (“Italian men are good lovers” or “the USA is a melting-pot”) but after a while it becomes clear that real-world data is often pointing in a different direction. The USA is a very well-marketed story, but underneath the Disneyesque veneer, as you’ve discovered, things are not what they’re purported to be. It’s salutary to read a lot of history, commencing of course with de Tocqueville and proceeding chronologically from there, in order to understand how the USA is so very, very different at a fundamental level from Western European societies. I think it’s this profound difference, which is so much at variance from the fanciful marketing pitch, that can cause so many European immigrants such a sense of disenchantment. The country has always been deeply corrupt, at least as much as Italy or Greece, for example, but unlike in Italy and Greece most US citizens are utterly unaware of the corruption and cynicism — they’ve bought the marketing pitch wholesale. But once we understand that money is everything and money buys power, it’s easier to accept the gap between illusion and reality.
It’s also useful to remember that many ordinary people, apparently decent, always collaborate with evil when it’s normalized. That’s because we’re a group species and standing apart from the group(s) we’ve affiliated ourselves with is too psychologically difficult. I know plenty of Republican voters who don’t agree with Trump at all, for example, but they all voted for him nonetheless because they self-identify as Republican. Not to vote for the Republican candidate, whoever he is, would simply be psychologically impossible for the ordinary person. And that’s how great evil thrives in the world.