Yeah, you're right, it's probably not (just) Hitler. Maybe it's that McCarthyism not only is a lot stronger in America but that it's also spread over to Europe somehow - because with Hitler ruling large parts of Europe, Communism probably wouldn't have been as strong as it was in our world, and McCarthyism wouldn't have had a reason to become so fanatical. Hm. I'd love to get some meta on this universe from the author.