Cuba can have their national autonomy, but other countries have no particular obligation to trade with them.

The primary "crime" which originally led to the imposition of sanctions on Cuba was that they nationalized assets owned by US entities without paying compensation. Now you could perhaps make a case that the Cuban government had a moral right to do that, but regardless of who was right of wrong it was certainly contrary to US interests. We don't want to set a precedent for allowing countries to get away with stealing US assets.