Question normal

It is very true that the CS is what it is today, cost and all that. I am a medical Doctor, working out of the US and i intend taking the USMLE. You all know, the USMLR is not for those who studied in the US. Students from out side the US too do sit for this exams and we know that training of medical doctors vary . So how can the US evaluate and manage these diffences in background clinical knowlege without a standadize test?