The entire US "race" discourse is pretty stupid, to be fair, too bad it has infected much of the rest of the world because of the influence of the US media.
(But I don't think "white supremacy" is a good way to think about the Nazis' hatred of Jewish people. They were white supremacists, but they hated the Jews for other reasons and if by some miracle they had abruptly stopped being white supremacists I think they would have gone right on persecuting Jewish people.)