Ethnic prejudice is a whimsical phenomenon, having little to do, in many cases, with real national security issues. Perhaps anti-German sentiment burned itself out in the World War I period, or maybe Germans-descended Americans were less recognizably German by the 1940s, or the Japanese issue was a distraction. Lots of factors.
George Templeton Strong, our diarist, is down on the Irish, not the Germans.
Not that I really blame people. I’d love it if we still showed some decent love for America. Today we are rolling over ourselves to prove we are NOT prejudiced against Moslems, which is actually a culture/philosophy that provably wants to kill everyone. Indeed, in my region they have boomed as our PC fools have slovenly given them everything they want.