I won't claim there is no racism in russia/USSR, but back when they were communist the state at least claimed to support a wide variety of racial and cultural identities. Mostly through force, and mostly against everyone's will (even the non-white soviet citizens), definitely not altruistically.
To contrast that with the US of the day, a country that just decided black people were people, they would have at least APPEARED to be the exact opposite of a white ethnostate. That is, if you want to be very generous with whom you deem to be white. Recent history tells us even the Irish, the "whitest" (colour-wise) people, were too brown for some. Are russians white? Bah, the ONE time you need to talk to a eugenicist.