To date, at least that I can recall, we've gotten four American characters played by Brits. Who did the accent best? Me, I'd choose Cohan or Lennie James. I often find Lincoln's accent overexaggerated, and with Morrisey, it almost seems like he's barely disguising his own accent. I guess the same might hold true for Cohan, but when I hear Morgan speak, in the few instances he's actually appeared on the show, I honestly forget he's faking it.