I have to admit that I personally prefer to say "Americans" over "United States of America ns". Maybe it's just because I'm lazy ... could of course call them "yanks" but that wouldn't be entirely correct either
As for Americans, if I am to assume that the ones I have met are representative for the nation, I would say that there are smart people and stupid people there as anywhere but that the general level of ignorance and arrogance (arrogance as in lack of humbleness) is somewhat higher there. Oh, and the people I have met have mainly been college students/teachers, people who are supposed to be the intellectual elite
Of course I may have been terribly unlucky in my choice of friends/acquaintances.
And as I said, I met some great people there as well, but if I were to draw an 'average line' ...