By Indirect questions, American English

Let's say that you want to speak everyday American English, not write a formal paper. In that case you would not go far wrong to use "whom" immediately after a preposition, "who" otherwise. Since the sentence initial position is never after a preposition (by definition of "initial position"),...

Dear moderators, May I ask you where do you all come from, i.e., Mr Micawber, Mr Pedantic (British?), CalifJim (American?) and Just The Truth? I have nothing against the British or the Americans or any other English native speaker, I just want to know the subtle differences there might be...