Communism failed everywhere... BUT most of those countries have started down the path to a more market driven economy primarily through external trade... its weird to have trade with USSR and China but not allow trade with Cuba at this time.
The embargo was never about communism itself, it was a response to the seizure of assets owned by Americans without compensation. I think these other countries either didn't do this, or at least didn't do it as much.
You're drawing a false dichotomy. Capitalism is good for a country regardless of trade arrangements. It's even better when you have trading partners, but you don't need them to reap massive benefits from a free market system.
Capitalism is really bad if you're trying to hold onto your dictatorship.
Cuba "opened up" economically before, in the 90s. They were under a lot of internal pressure after the collapse of their sponsor, the USSR. As soon as the economy recovered enough to secure the stability of Castro's ruling mafia (party officials, military, etc.), he reversed the market reforms and ratcheted up repression.
