American here, I've lived in the UK for about 15 years.
I'm just back from a holiday resort with a lot of American guests.
I noticed a lot of them didn't say please or thank you to the staff.
This is ridiculous. Americans are practically defined by their compulsion to continuously ingratiate themselves to wait staff.
Americans are, I think, friendlier, make friends more easily, have a sometimes rushed approach to intimacy (not in the sexual way), and are very, very loud.
The bulk of Americans can be slightly clueless about some basic international issues, like the controversy surrounding Israel or Tony Blair, for example.
Americans are generally more optimistic and possibly even more entrepreneurial, they have zero expectation of a welfare state so it wouldn't occur to them to complain about the council not giving them a refrigerator or whatever. That's not on their radar.
It's true that their social position is broadly defined by income rather than class, but the US still has its version of aristocrats who care very much about lineage.