Then elucidate. How did Castro “build a wall around Cuba”?

I think you mean the US has built a wall around Cubs using embargoes and sanctions, which has been unilaterally condemned by many rights advocacy groups - incl the UN.

You know, the US, whose own CIA is responsible for the overthrowal of many democratically elected governments and a fair deal of assassinations themselves?

Though they did try to assassinate Castro many, many times - and failed at every attempt. Some speculate that this is why the secret police of Cuba became so pervasive, leading to the government being able to hold on to power.

It’s like every time the US does an “intervention” they make things far worse than they need to be - and prove how incompetent they are in the process.