As an American, I agree. I think one of the factors is that it's easy for the US to be a world unto itself. With 325m people versus the EU's 505m (soon to be 440m), and with roughly equivalent GDPs, it's really easy for Americans to stay in their bubble. E.g., hear only English, experience only one culture, deal with only one system of law. We can easily move a thousand miles and still be in a place where, well, people measure in miles.

There's some hope, though. As recently as 1994, only 10% of Americans had passports. But now that number is above 40%. [1] Part of that's due to to no longer having passport-free travel to our nearest neighbors since the 9/11-inspired security tightening. But I think part of it's real.

[1] https://www.bbc.com/news/world-us-canada-42586638