There are no economic or security reasons to blockade Cuba, so that leaves *political*.
It used to be believed that bullies were low status individuals who are lashing out out of frustration. But research has shown that bullying is an effective strategy for achieving and maintaining social status. In other words it's a political winner. So the focus of research has shifted from the bully to the people around him who enable the bullying. The inner circle are the henchmen -- people without the charisma and daring to initiate the bullying, but join in when the bully gets things started. Around them are the audience, the people who wouldn't risk participating but enjoy the bullying vicariously. And around them are the much larger group of bystanders, who don't approve but are waiting for someone else to stop the bullying. Then off to the side are the defenders, who stand up to the bully.
Perhaps the least appreciated supporting factor in the phenomenon of the high-status bully is the silence of the bystanders, which is dependent upon the perception of widespread approval. Since you can't visibly see the the line between the approving audience and the apalled bystanders, the silence of the bytstanders is absolutely essential in sustaining the bullying.
Lot's of Americans are apalled at the idea of using military force to inflict suffering on the Cuban people. But that's only politically advantageous *because* of *them*. Tney are indistinguishable from the relatively small number of people who are thrilled when Trump announced he can do anything he wants wtih Cuba. The gap between actual approval and *perceived* approval is absolutely critical in establishign and maintaining any kind of authoritarianism. This is why would be authoritarian leaders are so focused on punishing and marginalizing any kind of expression of disapproval.