I think TP describes accents where they are appropriate quite well. XXXX has an obvious Australian twang to it etc. I'm not sure if he's dared to ridicule the American accent but I dont believe so. The type of words used by people in A-M are also very British. Buggerem is one that comes to mind.

Having said all that I personally dont have a problem with american accents or americans playing roles in a TP movie. America has some fantastic actors.