Well, I can’t really say a whole lot for the U.S. knowledge of their own country, much less other places, since my brother once had an Honors World Geography teacher who couldn’t distinguish Wyoming from South Dakota, and insisted she was right even when the students pointed out her error. However, I will say that I think it’s partly a function of sheer size and constantly being in the center of the world stage. Unlike Europe where crossing borders is a way of life, in the states unless you live on the Canadian border its expensive (both in time and money) to leave the country. Then you watch the world news, and 1/2 -3/4 of it is centered around stuff that is either happening in the U.S. or was done by the U.S.
Having said that, I still admit Americans really should pay more attention to world history and geography.