You are not mistaken. Consider this American WWII veteran:
General Eisenhower, Commander of Allied Forces, European Theater. His name means 'Iron Striker' in German.
Americans of German background were not treated specially in WWII, mainly because they were virtually indistinguishable from any other American. Same for Americans of Italian descent, as far as I know.
As for Americans of Japanese descent, I believe they were interned as much for their own protection as for suspicions about their loyalty. But I would never try to justify the camps with barbed wire. It's pure speculation what might have happened if they had been simply left alone by the gov't. Hatred of the Japanese was so virulent at the time that it might have gotten a lot uglier than the concentration camps. (Now someone is sure to jump into this thread with that old canard about 'FDR knew in advance...')