The majority of people,in my experience,who teach in the USA,have trained at the establishment at which they teach therefore they have FAA commercial instrument and cfi tickets-the question however has now been put on the other foot,as the caa/jaa have deceided to try and halt the teaching of JAA ppls in the states by FAA qualified pilots-a rediculous measure aimed at wiping out small fto's that slice into their profits,the figures of 500 total time with 200 as cfi has been put forward -i dont know many young instructors in england that have this -i know the majority of instructors in the states however have many more hours than this,my advice however is try and get a clear indication from both the JAA and FAA before venturing out here,as for the visa issue,you can instruct here on an m1 student visa but only if its a continuing part of your course of study