This refers to when Kruschchev, a Ukrainian, "gave" the Ukraine all its present territories which have a vast majority of Russians in 1954. Today's Russia has this perception of the situation whether propaganda or not.

As for the past centuries you are right. A look at the changing borders and empires that have come and gone makes for much confusion. What remains is the present day contention that does echo Hitler's claim over territories with a strong German "ethnic" presence, were it not for NATO enchroachment since the cancellation of the USSR. I suppose that if the Warsaw Pact were cozying up to Saskatchewan the US would be touchy, too.