[Charles Martel]

Interesting, particularly the mention of sailors and the War of 1812 (sometimes mentioned as a "minor theatre" of the wider Napoleonic Wars). According to the linked brief video below, the British accent morphed into the Virginia Tidewater accent, then changed more dramatically as it spread geographically.

It may be more accurate to think of the Virginia Tidewater accent as closest to the way the Brits spoke at that time, and that the geographical changes in the language weren't only in North America. Either way, port cities played a part in the evolution.

Southern Linguistics

[Cronos]

1812 was related to the Napoleonic wars. The USA is lucky that the hyper paper, the UK didn’t decide for revenge after waterloo

[packagingguy]

I went to university with a guy from Chincoteague Island. He had a friend who would translate what he said into modern English.