I can't imagine why it would make a difference - it is the same JAA syllabus taught by a JAA instructor and examined by a JAA examiner to the same JAA standards. The only difference is that you'll be doing it in an N-reg aeroplane and you won't spend weeks sitting on the ground in the flying school, drinking coffee from a machine and watching horizontal rain batter against the window. Caution though, there was a thread a while ago about FlyBe - they seem to want you to have done everything at one or two schools for some reason but I don't know if this is real or if it is, if it is still true.
I did all my ratings, licences and hour building at different schools both in the US and the UK (apart from the IR and Multi which I did together) and nobody passed comment. When I applied for jobs they were mainly interested in how current I was and if I had passed my skills tests first time or not.
I would be careful choosing your school though - there are good and bad schools in the US as well as the UK so you really need to go there and talk to the students before you commit any money. A short holiday visiting some of these places might well pay dividends and save you a fortune in the long run. A good search on this site will also be invaluable.
Good luck with your training!