Actually, getting an MD from outside of the USA puts you at a huge disadvantage for getting a residency (and subsequently fellowship) in the USA. So in that sense, yes all USA MDs are pretty much superior to any international ones. It's less about "pedigree" and more about residencies preferring students from the USA schools much more heavily.
That doesn't mean there aren't many international grads that are US doctors, just relatively few. And it has gotten a lot harder than it was in the past few decades to be an international medical school graduate and train in the USA.
That is more dependent on specialty. There are going to be little to no international medical graduates (IMG) in dermatology residencies. This is the original quote I took issue with:
What are you talking about? So many people go to the US to study medicine just for the prestige.
In the context of this thread, regarding universities, that statement is bogus. Hardly anyone outside the U.S. should be considering to apply for a U.S. medical school, and the
main reason is cost. It makes sense that only 1,300 foreign applicants applied in 2010, with 171 matriculating (for 20,000 spots). That's a 13% acceptance rate. IMG performance in the 2015 Match for U.S. residencies, on the other hand, was 50% successful match for first-year positions by non-U.S. citizen IMG applicants. That doesn't include matches for mid-residency openings.
Even if your chances of getting a residency spot is lower as an IMG than as a U.S. med school grad, it's still higher than getting an acceptance into a U.S. med school.