I've not played alot of MP games, and for those that I have played, it's been on public servers. Generally in my experience very few people use mics. It just so happens for me that the few people who make gaming sense when they speak are British guys. But that's probably down to the servers I frequent.
I do think that the few times ive been pissed of by retarded yappers using mics, has been with americans. After all, they are globally renound for speaking their minds out loud, even if what they say is utter shit. (not evident in satis and shiny's case)