Despite being thought of one of them singer/songwriter types, I sing far more traditional music than my own. Other than two or three Australian songs, the rest are all from the U.S. There is no "U.S."
or "American" accent to sing in, and while there are regional accents and some differences in the way place names and towns are pronounced, this control is so mobile that if you go to Maine and walk in a store, you may well talk to someone from Pennsylvania. It's not that there aren't any regional accents but it's certainly not as pronounced as in Britain. I live in Connecticut, but grew up in Wisconsin and lived for several years in New York City. My wife was born and spent her first few years of her life in Georgia, grew up in Brooklyn and now lives here in Connecticut.

Education also tends to homogenize accents and pronounciations.

Whether I'm singing a song recorded by Clarence Ashley, Peg Leg Howell, Mississippi John Hurt, Charlie Poole or Almeda Riddle, it feels natural singing with my own mongrel accent. I don't feel any need to sound "black" on blues songs or the black gospel that I sing.
I sing songs, not accents.

Now, if I was singing something strongly identified with a British or Scottish accent, I'd mess it up one way or the other. If I tried to do a dialect, it would sound phoney as a three dollar bill, and if I sang it naturally, it would lose a lot of the character of the song.

That's why I stick with what at least to me sounds alright singing in my natural voice.

Jerry