Interesting question, Andrew, given there could be several wrinkles associated with a Brit AND U.S. registered boat plus dual citizenship. Will you be Crossing in your boat and therefore arriving first in the
Caribbean? And how is your boat "registered" in the U.S. - presumably USCG document? And what comes next - onward to the
Canal?
If your A to all those Q's was 'Yes', I'd recommend a
route up thru the
Bahamas to the USA's
east coast, do your visiting there, and then circle back down to the W Caribbrean via Cuba's N and/or S coasts. I say this because I wouldn't have complete confidence that U.S. citizens on a U.S. boat can visit Cuba with impunity, no matter your British citizenship and boat
registration, and of course you would be clearing into the U.S. on your arrival - no matter what flag you arrive under.
It's also an interesting puzzle that you are looking for insurance coverage for both USA coastal and Cuban coastal waters, as those coverages are often mutually exclusive - Pantaeneus being one such example. Is full coverage a requirement for you while in USA waters? After all, the weather's pretty benign and there's an inland waterway all along the east coast...so another option for you to consider is binding coverage with Pantaeneus and supplementing it with liability only coverage for the period you visit the USA. Alternatively, and if your stay in the USA is an extended one, you could hop between policies altho' (re)survey requirements and premium costs may make that unpalatable.
Jack