My daughter was born in Thailand, we moved to the US in 2018 so she could learn to sound like an American. I was told that Thailand schools prefer American teachers for English as other “English” speakers have pronounced accents.
Heck, if you ever listened to Brits, they all sound different. Worth watching “My Fair Lady” to hear that.
It's a regional thing in Britain. I like to explain it in this way..... we have different regions here. It's the difference between a Minnesota, Georgia, or Texas accent.
Throw NYC in for good measure. But even in the northeast, the accents differ.