Answer:
Just about everyone was back then. The American military was segregated and Japanese people were forced to serve to earn their freedoms from the "relocation centers" that were essentially American concentration camps. The SS, Hitler's volunteer army, wasn't segregated. It consisted of Italians, Muslims, Turks, Astrians, Mongols, Germans, Jews, Britons, and more non-Germans.
The better question would be: "Why was America so racist?"