I don't think paganel's claim is that all race discourse is derived from the US. Rather, that (1) the race discourse in the US is stupid and (2) that much race discourse elsewhere these days is derived from the US's and is therefore similarly stupid. (Other independent race discourse might also be stupid but in different ways.)
Race discourse in the US is not stupid. Nazis from Germany mass murdered people because of white supremacy before US critical race theory. It's important to talk about Nazis and white supremacy instead of ignoring the problem and hoping it will go away by itself.
It is possible for something to be important to talk about, and for the way it's talked about to be stupid. In fact, I think it's quite common. I agree with paganel that a lot of US race discourse is stupid. I agree with you that sometimes it's important to talk about race. There's no contradiction between those.
(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.)
