> Parts of Poland were annexed by the soviets and became part of Ukraine and Belarus

I don't want to touch that hot potato, but that region was extremely diverse, with a large Belarusian, Lithuanian, Yiddish (before WW2 sadly), German, and Ukrainian speaking populations. I don't think any ethnic group had an actual definitive majority in that region until after WW2.

Completely irrelevant to whether the Polish language and cultural identity was suppressed. Most of historic Prussia is now part of Poland. No one claims that German was suppressed in East Germany.

Well yes but people who identified as Polish (e.g. upper/middle class and urban residents) were deported or a given a chance to leave west.