>That's why the US doesn't have a migrant integration crisis like the EU does - we know how to welcome and inculturate people
I believe you got this other way around. The US doesn't have a migrant immigration crisis like the EU does, because it's a big isolated island with relatively strict immigration policy. The people who immigrate to the US are exactly the kind of self-motivated workers who do the integration work themselves.
Many here believed that investing in integration will magically make open borders policies work, and the countries did. Less people in Europe believe it now.
Another thing is, how much immigration does US get? In Europe, many countries can have a significant fraction (a few percent) of their population immigrate over a few years (for example check how big UA immigration was). That makes integration much harder.
To be clear, I'm not against immigration, but it's a complex topic and I believe you're a bit too optimistic and extreme about it.
>For the sake of full transparency: I'm an open borders maniac, which makes me left wing by American standards and basically persona non grata in Europe.
I don't get dividing people into two neat categories (left and right). And you're welcome in Europe, it would be great to have you and I'm sure you would do well here!