They understand the general language but more obscure words, and slang they cannot understand for obvious reasons. And no, the questions about British stereotypes rarely pop-up and are always a joke.
The questions are normally about things in Britain. Things that people from Britain take as normal but are not in America. Like the raised up concrete bumps on the paths either side of the crossing to tell blind people they've crossed the road. All my American friends ask about them.
It's interesting to see Britain from their point of view. All my American friends love Britain and love the British. And I like Americans - all anti-American, and anti-British sentiment in anyone from either nation is bull. We're the two greatest allies in history and always will be. But you'll always have those idiots that go on about Britain's Empire being evil and then British ones going on about America ruining the world ...
Even if they are loud mouth yank bastards! Yeah, you come to the war late and say you won it!