Americans like to think that but outside of that US/UK bubble Americans rep is not clearly so clean.
This idea that foreign MMA camps were full of PED users and the US was somehow clean really does not bare out any serious analysis, a pretty high percentage of those caught on PED(or very likely on them) have been American and a lot of the rest have been foreign fighters training in America.
I would say part of it comes down to how PED culture manifests, in places like Russia and much of eastern Europe you have more of a history of state controlled PED use but MMA fighters tend not to be involved with state programs, there often people who fell though the cracks of sports like Judo, Wrestling, Boxing, etc and ended up in MMA(often via Sambo who is very small scale). Not to say there isnt a good deal of PED use in such camps, I suspect there still is but I think the "Russians Dope" rep really relates more to athletes who get into Olympic programs.
The US by comparison I would argue that PED use is much less linked to public bodies, maybe testers might turn a blind eye(espeically back in the 80's) but the actual PED use tended to happen in individual camps and perhaps as importantly in gyms generally and even in collages or high schools. I think that carries over into MMA much more as MMA camps are much more similar to those enviroments or indeed actually part of them and they share the same PED culture.
As far as cheating generally I think that is rather more generalised, I mean its not like we haven't seen some massive cheaters from outside the US. Maybe you could argue that the jock mentality and wrestling being very much about winning from the start foster that a bit more than some other arts with more of a traditional MA tradition?
