Hi YannMo and welcome to the forum.
First to clarify. I believe you are thinking about two different documents. A title is only the document showing
ownership of the boat. You will also need some form of
registration which is like the
license tag on a car. It is very easy for anyone, even non US citizens to get both of these in the state of Florida. You should also know that in the
USA there are two ways to register a boat.
Registration with a state as already mentioned or federal registration through the US Coast Guard which is correctly called
Documentation. Documentation is not allowed for non citizens and if you buy a boat that is documented you will have to go through the process to remove the boat from the USCG system and then get state registration.
Since the boat will not be USCG documented there is no concern about them canceling your documents. Also I don't think there is any problem with Florida for this.
Regarding Cuba I cannot say what documents they require for a boat but I do know they are welcoming yachts and would think any official paperwork would be acceptable.
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