I guess that explains why I never see many French tourists in Thailand. Americans tend to be over conscious of the "Ugly American" stigma and as a result, I seldom see a bad American tourist except the drunks (in any nationality, they tend to be jerks). Of course, I am an American and may be discounting their shortcomings, but I don't think so. Japanese are very polite but Chinese are often rude. Australians are frequently a little wild. Germans seem afraid of being cheated and Canadians are always afraid they will be mistaken for Americans. British are great with locals but critical of Americans.
My stereotypes for what they are worth -- nothing.
Before my wife and I took a trip to Ireland we read a book called "Keep to the Left" by a Minnesota man about a trip he and his wife made to Ireland about seven years ago. He made frequent accusations of rude Americans he met on his trip. So we didn't know what to expect. In two and one half weeks going around Ireland, including five days in Dublin, we didn't run into one American tourist that resembled the rude Americans the man (college professor) from Minnesota claimed he ran into. I'm not saying they're not out there, I'm just saying we didn't see any rude Yanks while over there. And yes, we did run into a number of Americans there.