Sanctions haven't harmed Cuba's economy

This column in Slate does a decent job of explaining how Fidel has kept his grip on his dicatatorial power. I have a real disagreement with the silly conventional wisdom:

Sanctions have accomplished three things since they were first imposed in 1960: They have inflicted hardships on the Cuban people, they have strengthened Castro's ability to block citizens' access to the resources they need to win some independence from their government, and they have alienated U.S. allies whose companies are penalized for doing business in Cuba.

Total BS.

Cuba's economy did not go in the toilet because of economic sanctions by the US. It went into the toilet because the communist command economy was not able to produce anything worthwhile for people to trade. Other nations around the world engaged in trade with Cuba. Nothing stopped the Cubans from trading with Canada or Europe for anything they didn't get from the US. The reason very little trade took place was due to the failure of the Cuban economy to produce much of anythng that Europeans or Canadians want.

This is just too simple to understand for so many people to screw it up. If Kroger should refuse to sell me groceries, I would still eat just fine as long as other grocers will sell to me. Kroger, by itself, cannot cut me off from trading my dollars for food. And the US didn't cut Cuba off from trade with other countries. The US sanctions, as a matter of simple logic, can not have caused the horrible economy that Castro's rule imposed on the Cuban people.