[nolatom]

In the States, no government license (read: Coast Guard operator's or captain's license) is required unless you're carrying passengers of freight for hire (meaning you're making money for the trip). So you can sail wherever you like if you're just carrying you and a crew, and they're not paying for the trip beyond just sharing expenses.

There are private certificates from private organizations, like ASA, USSA, or from England, the RYA. But they're just that, private, not public. Charter operators and insurance companies may like them, but they're not mandatory as far as I know.

But I recall the words, "sailing round the world" in your question. For that you need much experience. The private certificates can be evidence of that, but these certs are the creature of the last two decades or so. I'd think some long-distance sailors have the experience, but no card or license to show, nor is one required.

If I'm wrong on this, I'd welcome being educated by those who know better.

 

[nolatom]

I kind of doubt that if you arrive intact in the Azores after having left Bermuda, Bahamas, or Caribbean, that they're going to demand some certificate of competence. You've already demonstrated competence by crossing an ocean and getting there.

That said, I think the advice above is good, you might as well get whatever certificates (public or private) you qualify for. Can't hurt, might possibly help.