It is probably for the best that those countries do not share borders.
I mean, fuck. A nationalistic government that would still have nukes sharing borders with Great Satan? And the terrain just so happens to be very resource rich and was recently sold for peanuts?
World's better without that kind of noise.
If the U.S. had bought Siberia the border between American Siberia and the remainder of Russia would be separated top to bottom by a 90+ mile wide natural border, the Ural Mountains. For practical purposes there would be a substantial barrier between the two nations. Good fences make good neighbors.
Also, the U.S.and Russia already share a land border.