I have just read some of the most ignorant statements from both sides.
1) You cannot really compare the UK and the US systems because they are completely different. US training is a graduate program, while the UK one is a 6-year undergrad program. There's merits and cons to both.
2) The information learned is pretty much the same everywhere you go, no matter if you go to east bufu school of medicine in Sri Lanka or to Cambridge / Harvard. The information currently known is universal, one country doesn't know more than another, etc. Different places focus on different aspects of medicine, perhaps (the aussies like a more psychosocial view of medicine, for instance), but general education is the same. Cambridge graduates are equal to any med graduate in the US, but so are graduates of Australia, Ireland, Israel, India, France etc etc etc. Medicine is one of the most prestigous courses of study worldwide, so you'll find extremely intelligent people coming from every single school possible.
3) The differentiation happens AFTER MED SCHOOL. THe place where regional excellence (or lack thereof) is evident in residency training, when you actually get into the work field. The US right now happens to have the most advanced technology and money to support medical technology/progress, so those who complete residency training in the US might find themselves more experienced or "competent" docs than those from say...yugoslavia. This occurs just because of a difference in exposure. However, to get INTO a US residency, everyone has to take the USMLE Step 1, Step 2. And currently, FMGS have to take the CSA and the TOEFL (although they're talking about making USMGs take the CSA).
Because they have to, FMGs usually way outscore USMGs on average, on the USMLE 1 and 2's. THIS shows that THERE ARE NO obviously SUPERIOR MED SCHOOLS universally, and that those who do well enough on the USMLEs to get into residency obviously came from schools who train their students well enough to be considered EQUAL to US schools. US Schools are in no way "better" than anywhere else, and other schools are not better than US schools. IT IS NOT WORLD CONSENSUS that US med schools are the best. That's just plain ignorant. It is well-known that US opportunities and technology may be the best, but that has nothing to do with medical schools themselves, just possibly indicative of residency training. The French think their schools and healthcare is the best. So do the UK schools. So do the Dutch schools. So do the Japanese schools. It goes on and on. Each school thinks it's the best, when they all offer pretty much the same courses.
There's a difference between being really proud to be American and being arrogant about it. I love that I'm American. I'm also completing med studies in Ireland because I found that their system of education is more suited to me than the American system (I actually could not envisage myself being very happy if I stayed in the US for med school). And I hope to do an elective at Cambridge.
The motto of all this is: don't say stupid s***.