Still, I think, that Japan directly attacked the US at Pearl Harbor made a big difference. Germany was also seen as having a bad regime with war criminals, but

Still, I think, that Japan directly attacked the US at Pearl Harbor made a big difference. Germany was also seen as having a bad regime with war criminals, but they started the war with the US not with such a carnage. So, I think politicians and parts of the US people in this time saw Japan as the worse "beast".