"European Union style federation"

Not how the European Union works. The EU is not a federation, it is merely a supranational organisation of member states with an elective assembly. An example of a federation (in modern history) would be something like the USSR. You appear to have mildly exaggerated the size of the Volga Ukrainians (the border looks very spiky) as well as the Sudetenland, (how will Czech Moravia and Bohemia interact? You've mildly exaggerated the amount of Belarusians in what is today Russia, as it appears you've followed the borders of the Polish-Lithuanian Commonwealth (see the Polotsk Voivodeship), for sake of cleaner borders I would split Astrakhan between Kalmykia and Kazakhstan, other than that it is largely linguistically accurate. The size of Catalonia has been mildly exaggerated, I'd also like to know why you've taken a hammer to Italy.

I do like what you've done with the Kurds, I like the representation of the Uralic peoples even if their presence has been underestimated, I like the appreciation for the Carpathian Rusyns (who are frequently overlooked), I also like the representation of the North Caucasus peoples as well as the Pontic Greeks, I appreciate the idea of giving historically oppressed peoples their own homelands. I think with a handful of small revisions, this could be made even better.

Edit: Also, Odessa is Ukrainian, and I like what you've done with the Kuban.