I spent LOTS of time in Europe over the last 4 years and I've found a majority of them to be very respectful and great to talk to. You'll be surprised how well they speak English and have an understanding of American politics.
Consider the reverse, if I asked people to speak German and discuss the current German political situation, we Americans would be mostly lost.
I think the biggest complaint I got from the Europeans, in any country I went to, had to be that many of them think that we, as Americans, are generally uneducated about our national history and role in the world. Argue for or against that as you will, I personally agree that some of us really need a refresher in American history.
My only advice when going to Germany is just be relaxed, and if you get to talking with some German citizens about politics or history, NEVER mention Hitler or the Nazis. You have no idea how pissed off they get.