But there's a nice symmetry to bringing up the illegal US occupation of Guantanamo Bay in Cuba. The main concern of Russia is maintaining its Black Sea Fleet at Sevastopol. Would they like to see a US-sponsored Ukrainian government had over the Crimea to NATO? We used to be regaled with horror stories of "creeping communism" during the 1950s-60s cold war days. Now we can see, since 1989, that there is a creeping NATOism.
Just in terms of great power politics it's easy to see that Russia has some reason to be concerned by the USA/NATO encirclement that has been going on. Historically Russia has more of a claim to Crimea than the US has to Cuba. Though this isn't for lack of trying on the part of the US.
In 1898 the US sent (uninvited) troops to "help" Cuban rebels oust the Spanish colonial regime. While Cuba nominally became a free republic in 1898, in 1903 The US strong-armed Cuba into approving the Platt Amendment to Cuba's constitution letting the US militarily intervene in Cuba whenever it saw fit. That same year the US was given an indefinite lease on Guantanamo Bay to establish a "coaling station" for its navy. The US used the Platt Amendment to invade and occupy Cuba a couple of times (the first was 1906-1909) to prevent Cuba from getting too uppity.
Come the Cuban Revolution in 1959 and the new government declared that the USA's taking over of Guantanamo was a product of gunboat diplomacy and it should be returned, since it was taken by threat of force by the USA. The Cuban government has demanded since 1959 to the present that Guantanamo should be returned to Cuban rule and that the US was violating international law. Cuba has protested to the UN and refuses to accept any US annual payment for the dishonestly obtained lease.
Matters got worse when Guantanamo was turned into a prison and torture site for supposed Al Queda members captured in the invasion of Afghanistan (or from anywhere else that the US wanted to kidnap some alleged terrorist). In fact the very lease agreement that the US says lets it keep Guantanamo states that Guantanamo can only be used as a naval base, and not for any other purpose.
How vital is Guantanamo to the USA's military defense? Why can't Obama just say, "well, I guess you got a bad deal and now we are going to cut costs and get out of Guantanamo, so Cuba can exercise full sovereignty over its national territory?"