The causality is not obvious. For example, throughout the 70s and 80s, organizations shipping medicine and other supplies to Cuba were regularly bombed or attacked (e.g. Hispania Interamericana). Anti-Castro terrorist organizations (e.g. https://en.wikipedia.org/wiki/Alpha_66) operated openly in Miami.

So does Cuba lack medicine because they're communist? Or are they communist because the US worked against broad prosperity in Cuba, often very violently and explicitly, for decades before and after Castro?