Viet Nam has always been more Western aligned than otherwise, with their history as a French colony. They've always been friendly with the West but didn't want to get the full colonial treatment, with puppet governments that grow more corrupt each iteration, so the more aggressive hooked up with the communists in the 60s, thus the war. The aftermath didn't work out as well as they'd hoped so they're doing their own version of Communist government/Capitalist relationships, like China. Their government is quite friendly with the US but wants to keep an arm's length on policy. Quite understandable and quite workable from an economic stance.
Cuba got the shitty end of the stick in the mid 1900s with corporate and mafia entanglements that were propping up Batista so turned to the Russians, who really just fuck up everyone. The confiscation by Cuba of US interests (assets) when Castro took over, plus the Russian military presence, slammed the door on any real relationship with the US. Until Cuba's attitude changes, the US really has no reason to do anything special for them. Obama thought that he could get the Cuban people behind him. He forgot that Cuba's authoritarian and tries to be alert to any attempts to build organic popular support for a regime change. So...the leaders of Cuba choose to slit their country's throats, slowly.