https://www.seattletimes.com/nation-world/i-am-worth-it-why-thousands-of-doctors-in-america-cant-get-a-job/Here in the United States, after graduating from medical school, you must complete a residency in order to get licensed. Residency slots are funded by the Federal Government, and there have been calls for years to increase the number of slots. There are more medical school graduates than there are residency slots, so every year, a few physicians do not match up.
There are many foreign medical schools that are the equal or superior to those in the United States. A graduate of most foreign medical school in Canada, the UK, Singapore, Japan, most of Western Europe and some other schools throughout the world will generally have no trouble in qualifying for a residency slot in the US, assuming they want to practice here.
Then you have the medical schools in the Caribbean. They are held in disdain by the US medical establishment and you will have a lot of problems getting a residency slot. The majority of students at those schools did not qualify for admission to a US/Canada/Europe medical school and many of the graduates are not at the same level of competence and training when they finish medical school.
Even if the number of residency slots magically expanded overnight, these foreign medical school graduates from the Caribbean are still going to be at the bottom of the selection process. Their best bet is to seek an alternative route to licensure, such as Arkansas or Missouri, or to look at practicing in another country. Anyone who went through the admission and schooling process and now claims they were unaware of the residency issue is either fooling themselves or a dolt.
This is no different than graduating from a non-ABA approved law school; you will find it difficult to find a state willing to let you take the bar exam. But a lawyer who does not pass the bar/is licensed has better career prospects than a physician who cannot get a medical license.
Edited to add: I have known many people who practiced as physicians in their home country, and cannot qualify for licensure under the different licensure standards in the USA. They end up working as physician assistants, research jobs or the like.