Personally I've found Americans to be very kind, warm people.
Some of the politics and 'judicial' system make me want to gag though. Of course, by this I don't mean to say that everything in Europe is better.
I know one major problem, as other posters have pointed out, is that Americans are very insular.
Examples;
I was in Kansas on a teaching exchange. A junior year High School student, knowing I came from England, asked me if the American TV programs on British TV had subtitles. I laughed and she looked confused; I had assumed it was a joke. She preceeded to ask what language we spoke in England, to which I replied ENG-land, ENG-lish.
In a Junior High School, a science teacher (also the school coach) asked me straight out what language we spoke in England.
I was in the USA during the LA Olympics. If the USA weren't in with a medal chance you didn't see any coverage of the sport.
In American newspapers (some of which are very fine), 'World news' is generally a joke, a few inside pages.
The thing is Americans CAN be insular, without it really affecting them (aside from English exchange teachers having hysterics when asked damn fool questions).
As far as language goes, in '95 and '96 I acted as a student guide for International students attending my University in England. This was pre-Austin Powers, so Americans has no knowledge what-so-ever of English slang.
Thus I had the opportunity to give (unofficial) language seminars on the big difference between snog and shag, what wankers and bollocks meant, and how you could say 'Jesus fucking Christ' loudly in a public bar without getting stared at by offended Christians.
The English swear, a lot. Swear words are virtually unknown on American TV. On English TV they don't cause the same issues.
Don't let the 'Enlish politeness' rountine fool you. English people ruled about half the world at one point, and although there were a good few battles along the way, most of it consisted of being nice and polite until the incumbant rulers realised they no longer had any real power, and then writing them a polite three page letter which actually said 'fuck off', but was so polite you couldn't quite put your finger on why it bothered you so much.