Cuba enjoyed massive support from the USSR for decades and it's still an economically backwards shithole. All the US does is refuse to trade with them.
Wow, sanctioning a country to hell, by the very closest trading partner who pretty much holds an inordinate amount of sway in the entire continent and in the entire world no less regarding trade deals sure seems innocent the way you put it.
It's not like average Cubans suffered and the powerful were protected. Surely it wasn't stupid gesturing brought on by grandstansing politicians who were looking for more circus to their bread. Surely not.
It surely wasn't another vein attempt by US politicians made to foster an internalised rebellion, that never took off, because Cuban secret police held the fort. Surely it wasn't all a huge, worthless game, that made ordinary Cubans suffer most of all...
...because that would be dumb posturing. I mean backwards, brain-dead, completely moronic, inhumane and unethical use of power.
The US is not obligated to trade with any country. And no action the US ever took posed a serious threat to Cuba or the Castro regime. The poor economic state of that nation is largely because of mismanagement under socialist economic policy. They have plenty of trading partners, they just don't have a developed economy because communism doesn't lead to economic development.