Actually, I believe there were internment camps for German Americans during WWII. Like the Japanese Americans, even some US citizens were interned. But the number of German Americans interned was a small fraction of the number of Japanese Americans.
Still, the Japanese were depicted much differently than Germans. I suspect the attack on Pearl Harbor had a lot to do with it, and the government's internment of so many Japanese Americans as enemy aliens didn't help.
Comic covers reflected that (I know it's already been posted, but I like the cover).
Though Fiction House covers tended not to depict the racial stereotypes that most other publlishers did, I think they still were more than able to get their feelings towards the Japanese across!