What an ignorant premise for a thread. First of all, there is more than one American accent/dialect. Second of all, most of the dialects in the States are derivatives of English dialects. For example, the "New York" dialect is almost the same, mechanically-speaking, as standard-English. Finally, I'm hard pressed to recall one example of an authentic-sounding American accent in the game...
'New York' dialetc is almost the same, 'mechanically-speaking??', as standard English' -
first off, what the hell does standard english mean? Do you mean Queens English? Secondly, the New York accent, as far as I can tell, sounds nothing like any English accent. If anything, the closest thing to any American accent in Britain has to be the Irish accent. Thirdly, what the hell do you mean by 'mechanically speaking'? I presume you must be referring to syntax?
Just because all American accents are derivative of British ones, doesn't mean they are in any way similar sounding - they clearly aren't.