Don't Americans make fun of Asian tourists with their cameras? Or Eurotourists and their aversion to daily showers? These things are natural built-in rivalries and levity, it's been going on as long as people realized they were even the slightest bit different than the other guy.
Germans don't particularly like Americans, but they don't particularly like anyone. The Italians like Americans mostly, they don't like Germans. In fact none of the Euros like Germans, they are way more disliked than we ever could be. South Africans love us, Eastern Euros like us, Irish love us, Brits tolerate us like we tolerate them, and if you make an effort with teh French they are extremely open and engaging.