I think that television and, before it, radio have done a lot to standardize North American English. News personalities almost all speak in a manner that minimizes regional accents.
I remember when I lived in Boston, you'd often hear the Boston accent when you were among people, but most of the TV commercials, even for local businesses, had typical Midwestern US accents, not Bostonian ones. Same with the TV news anchors. I was told that to be a news anchor, you had to be coached to speak the typical Midwestern American accent and not show your Bostonian accent.
Now that I live far from Boston, I watch online episodes of This Old House
because I miss the accent.