Hi,

There is only one degree that you get in US for Medical education that is MD and after that you directly go into residency program after completing your internship. Once in residency, you further move ahead to choose your field of specialisation to become a specialist in a certain field. USMLE is given at the end of medical education by students willing to get into residency program on the US. Also you study in your residency program for your specialisation and no other degree study is required to be done separately.

I hope this helps.

All the best.