I've been fortunate to visit America a number of times over the past few years. Always had a fondness for the yanks since I was young.
On all my visits I have never encountered a rude American, always found them very friendly and helpful.
I hope none will get offended if I share a little of my experience. During my younger years of visiting the U.S., there were many hospitable Americans I met. However, I've encountered a few times of being offended because of my yellow Asian race. Americans cut in line, get your cab, talk in a demeaning tone etc. It's quite easy to blend in America if one is Caucasian/white from another country than an Asian with small eyes, regardless of how big you are. I simply let it go most often, not out of fear, but out of respect in being a visitor in your country. I believe the laws of good yin yang, karma (or whatever it is one believes) will eventually turn.
There is a feeling of entitlement among a few Americans, that the world owes them. Fortunately, not all are like this. I was surprised that during the times that I actually needed help, help came from 'unusual' people. Example, years ago I rented a car and drove across a few states for business. The car broke and guess who helped me? Two black Americans. I was never more appreciative of help from strangers. Another time, my companion left her bag and mobile at the resto. The ones running to us across the crowded resto to return these were uhm, not Americans, but actually Australians.
I'm just thankful that most here are the most level headed people anyone can encounter. I think it was Wiz who correctly say that it's the individual persons that give you a better impression that the country as a whole.