My sister goes to France every year to visit her in-laws. She is not only American, but of Jewish descent. Every year I get more and more concerned for her safety. Being the liberal she is, she used to scoff at my fears. Not after her last visit, even she was shaken by the muslim's growing open hostility. Her french is flawless and she is often mistaken for Belgium, an assumption she used to correct. She no longer corrects it.
I lived on the west coast of France in the 70's. It was idyllic in the countryside and even in Paris I felt well received (spoke French fluently). I remember worrying about the stigma of the "ugly American" but never felt its sting. I think I'll let those memories linger.