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human
ELI5 : How did accents develop for peoples who speak the same language in different regions?

From England to the southern USA to New Yorkers to Canadians and more, all of which have a populace that speak English with a different "twang". How did this happen? They all have different slang which I can understand, but the actual delivery is so distinct.
gpt
You talk like the people around you talk. 

North American English diverged from British English over a century before Australian English diverged from British English. 

Therefore Americans and Canadians sound less British than Australians. 

In the centuries since those splits, though, regional accents have taken on lives of their own and moved even further from whatever baseline there ever was. 

Which is purely abstract since there is no baseline and never was. In Britain, the accents are extremely pronounced from one region to the next. Manchester, Liverpool, Cockney, Cornish… they all sound very different because people from Cornwall aren’t talking to people from Newcastle on a daily basis. 

Again, we talk the same way the people around us talk. 

The smaller the bubble, the more unique the accent. 

Big metropolitan cities have people with all sorts of accents converging on them, so they tend to blend together and neutralize one another. Those are big, diverse bubbles so there’s not really a pronounced accent.

On the flip side, a rural town deep in the American south isn’t likely going to have many outsiders visiting, so the bubble is much smaller, and the accent more up distinct.

There’s even an island somewhere on the Eastern seaboard that has remained so isolated throughout America’s history that they pretty much still talk like they did in Colonial times.