Ask any European who lives or works in a major tourist destination. Many American tourists are wonderful, but the worst of the bunch are atrocious. The yahoo tourists openly mock the local culture, they ask for prices in dollars, they wear yoga pants and tank tops in cathedrals, they get offended when the locals don't speak English. It really isn't unusual to hear someone loudly complaining about how awful everything is and how much better things are in America.
Some American tourists seem to have the attitude that American culture is objectively correct and that the rest of the world is essentially a theme park with bad service. The "USA, USA, USA" attitude doesn't travel well. It's an attitude that quickly melts away after real immersion in a foreign culture, but unfortunately many Americans don't have that luxury.
It isn't a new problem - see this wonderful 1943 training film for American troops being stationed in Britain: