AR,
You can apply for a visa for flight training in the US. Many people do this. There are schools where you can stay on as a flight instructor building time towards the ATP (not ATPL in the US). There are people here who are knowledgeable about the various visas.
In general, unless you have the right to live and work in the US, you will not get hired to fly for a US airline.
I would expect that medical school counts as the four-year degree.
Good luck!
Terry