Here's my favorite fallacy regarding Cuba. The American embargo has nothing to do with Cuba's economic woes. Cuba has the rest of the world to trade with, Russia, China, Iran, North Korea, Venezuela, Brazil, Spain, France, Germany, Italy, Britain, Canada, Mexico...should I go on? Trade with the U.S. is not the sole arbiter of economic success on the globe. While the USSR was able to prop up the Cuban economy for a while, the weight of the USSR's own totalitarian system ultimately collapsed under its own weight.
One thing is certain, Cuba's inability to prosper in trade with the rest of the world is due to the fact that Cuba produces little of value. It produces little of value because its people live in a vacuum of civil, political and human rights. It is a totalitarian state that seeks to preserve its own existence by claiming to provide the basics of life to its citizens, although in fact it only keeps its citizens on the borderline of abject poverty and submission.
Cuba could be a wealthy, prosperous nation, with or without American involvement, if its citizens were free, with guaranteed civil, political and human rights.