You can sit the steps and then become licensed in most but not all states. Some states require accredited postgraduate training in the US. FSMB | State-Specific Requirements For Initial Medical Licensure
Then you could find a job without being board eligible, which is difficult but not impossible. More likely you would want to be board certified, for which you would most likely do 4 years of fellowship, which could be in different subspecialties, could include one year of research, and must include four months of nuclear medicine. This is called the Alternate Pathway of the ABR. It is possible, but unlikely, to fulfill the requirements of the Alternate Pathway by doing four years at an academic faculty position at an institution with an accredited training program. You could also do residency again, in the US.
If you know you want to work in the US, you might as well apply to residency in the US now.