Since I started this thread, may I finish?? Although I've encountered some very poor PPL holders who had done 'quickie' courses in the USA, I am quite prepared to believe that there are equally some very good US-trained PPL holders - it's just that I haven't yet met one, but that's as may be.
Incidentally, I also encountered a UK-trained PPL holder last year who wanted a check out but didn't even have a valid licence as her CofE was out of date - although she had done some recent flying. We thus launched off to do a GFT - and her flying was so poor that, apart from the fact that she failed dismally, I would have serious doubts about letting her have command of a wheelbarrow - and certainly not a bicycle!!