I appreciate your point about racism being different from ethnocentrism but I'm a little confused at some of your other points. You say Asians are White at one point but you also say Asians are Black at another? By the way, I am not a White person (you seem to address me as such) and I identify as a person of colour. I do not see myself as White and I think most White people I have encountered, if not all of them, also perceive me as a non-White person of colour. Which means I do not get the privileges of White people in the White-supremacist society I live in.
You bring up historical context which is good to know, but at the same time I think we should focus on present-day perceptions of race since it is present-day problems we're trying to solve. In places like the modern U.S., there are White Europeans, Black folks, Indigenous folks, and other people of colour (Latinx, Asian-Americans, etc.). To make things simple for people, I think that's all we really need to establish.
In terms of racism vs. ethnocentrism, I think that's an interesting idea but a nuance that most people would not be able to (or bother to) understand. Perhaps let's just focus on stopping prejudice based on appearance? As an Asian person, I know there are people in my community who will be prejudiced against anyone of darker skin colour, whether that's a Black person or a slightly darker South East Asian person. Whether that's racism or ethnocentrism or colourism or whatever the correct term is, it's wrong.