What you may believe and what the realities are, are quite different. You see, many Russians were born in Ukraine, as it was for many centuries, a part of Russia. Especially Eastern Ukraine.
You should view these ex-pats as becoming so by way of land historically belonging to the U.S., suddenly becoming a part of Mexico, like say Texas, to put it more like what is occurring in Ukraine today. That these ex-pats, like these Russians, have lived there over many generations and that is their home. For them their home is part of Russia.
If you had even an inkling of history with regards to Ukraine, you wouldn't have answered so flippantly.
“You should view these ex-pats as becoming so by way of land historically belonging to the U.S., suddenly becoming a part of Mexico...”
Yeah, well, that’s not the scenario you came up with, so too bad. Think it through a little more carefully next time.