NeutiquamErro, Thank you for taking up the task of explaining this fascinating subject to our transatlantic cousins. You have done so most eloquently.
I had no idea that the range of accents in England was unique. But it always did fascinate me that the 15/20 sq mile area which includes Newcastle, Gateshead, Sunderland, Ashington and Hexham, contains four distinctly different accents. Although even Americans may not call Geordie a ‘British accent’, it would probably confuse most southerners.