I hear that all undergraduate credentials are evaluated and confirmed before licensure in any given state, even if you successfully completed:
-MD degree with ACGME accredited clinical rotations in an approved foreign medical institution
-ECFMG certification + USMLE III
-US residency with the board ceritification

I'm not so sure what these pre-medical requirements are at state level (minimum GPA? minimum semester hours? MCAT? etc). It would make sense for medical schools to set their admission standards accordingly, but with Caribbeans, I can never be too sure.

Any ideas?

From what I have learned - most states require that applicants for licensure have completed at least 90 undergraduate (or pre medical) semester hours. This is usually not explicitly stated in the written law, however what is normally stated is that the final decision is at the descretion of the state medical licensing board - some require certain classes, some require certain hours, etc. I suggest that you personally contact the state licensing board in the areas that you are specifically interested in.

Most states require applicants to have at least 60 credit hours completed at an undergraduate institution (before medical school) but don't mention any specific subject requirements.

Well, as I'm currently in the process of applying for my NJ license, I can let you know the ton of paperwork that they require

1. USMLE scores
2. ECFMG verification
3. CV
4. Official transcript from undergrad (They require 90 undergrad hours and documentation that you've done at least one course in Biology, Chemistry, and Physics)
5. List of all your clinical rotations, including preceptor, hospital, and dates (since I went to Saba and did my rotations in a site "geographically distant" from my basic sciences)
6. Copy of my diploma
7. Paperwork from my current residency, malpractice, etc.
8. Criminal history

It's definitely a hassle. And this from NJ, one of the most IMG-friendly states there is ...

Tony