"Imperialist Communist dictatorships try to destroy the identities of conquered countries and 'foreign' internal regions, including the USSR and China (Tibet, Xinjing). That fails spectacularly - when the USSR collapsed, all the ethnic identities reappeared."

I'm pretty sure this stuff happens in countries that aren't communist nor dictatorships, too. See the treatment of First Nations people in the US and Canada for examples.

That last line doesn't tell us much unless you can compare it to what happens in other countries: I'm guessing that in most places, the outcome is similar. And to be absolutely fair: My grandmother didn't learn Arabic because her mother insisted the children not speak anything but English. They had moved from Syria to the US long ago. Realistically, it was so they did not get treated badly. No wonder her children and grandchildren (me) do not speak Arabic.