Under Coast Guard you should have also listed that USCG personnel are by law Officers Of The Customs
and have the same authority (and in some cases more) as US Customs
. part of that is the authority to seize a vessel. But you do not seize a vessel without due cause. I had a vessel seized in 1977 (nothing to do with Cuba) and spent about 6 hours justifying it to our Chief legal
Officer. Not a position a LTJG wants to be in.
Also, some people do get authorization to travel to Cuba
(and spend money
while there). One category is cultural exchanges. Another is agricultural exchanges. A dirty secret is that most of the food
imported to Cuba comes from the US, and as a result agricultural exchanges are usually permitted. As was mentioned, families with relatives living in Cuba may now visit. There are some other exceptions to the ban. But the average Joe cannot just up and go without accepting the fact that if they are caught will be prosecuted. And if they go by boat
it is possible that the vessel could be seized, although it is rare and I haven't heard about a a vessel being seized for many years. But I have heard of many people being fined for going to Cuba.