"when no nation on earth could have come to Cuba's aid"
I was going to upvote up until that line. Maybe some of these countries would want to help:
"Cuba provides more medical personnel to the developing world than all the G8 countries combined"
"The idea of a nation saving lives and improving the human condition is alien to traditional statecraft and is therefore discounted as a rationale for the Cuban approach."
"currently educating more doctors, about 70,000 in all, than all the medical schools in the United States"
"US President Barack Obama commented... a reminder to the United States that limiting its interactions with Latin American countries to military and drug interdiction might be limiting its influence."
I'm not saying that any of these nations would have declared war on the USA or anything, but there are things that could be done to make a move like invading Cuba quite expensive in any number of ways. Cuba has a lot more friends than say Afghanistan or Iraq had. Millions and millions and millions of people protested the invasion of Iraq, could you imagine military action against Cuba???