There is a large Muslim population in France too, especially in the suburbs, locations of the riots and unrest from a little while back. Just something to think about.
I used to have an American flag patch on my back pack that I travel with, but unfortunately I had to remove it for my own safety during my travels. The one exception was when I was in Israel where most people seemed to like Americans. However, I was especially careful in the West Bank. Just be aware of your surroundings (situational awareness) and up on your current events and local culture. I've been chewed out, yelled at by taxi drivers in China, Turkey, waiters in France, Italy, Greece when they find out I'm American. Most of it is because they don't like our government (i.e. - George Bush) so they take it out on the people a bit. I was wearing my UCLA t-shirt in Paris when I was chewed out by a French guy. For a guy who supposedly didn't speak English, he sure knew how to curse.
Another time I was in a Turkish bathhouse and the guy had me tied up in a knot then asked me,
"You are American? Your name is George? Like George Bush! Do you like George Bush? Are you like George Bush?"
Seeing how he had me in a guillotine/arm bar what could I say? I was like of course not. Then he was like, "I like you George" and proceeded to knead, pound the crap out of me (it's a Turkish massage).
However, I always try to be on my best behavior and treat everyone with respect. I am representing my country after all. I get a lot of good vibes from people and I am very helpful. They always seem so surprised when I tell them I am American, but it does help to change minds. That's soft power for you I guess.
Common sense, courtesy and awareness will serve you well.
Enjoy your travels!