It's a fact that when the provisional constitution was presented to the convention in Montgomery one of the first objections was to the name - Confederate States of America. Attendees thought it was too limiting.
The Confederacy was 'born' with the plan to expand to points south. All the better to spread slavery.
You didn't answer the question. If anything, you affirmed that none of those places were part of the United States.
And there was already massive slavery in the Caribbean.