That's interesting, too. Hadn't seen or experienced that. After I posted, I realized it is possible to change one's accent. Which was the nightly news Canadian, think it was Peter Jennings. His speech was just like midwesterners.
Somehow those of us who have ancestors from anywhere do no longer speak like they probably did. Going back to the 1600's in New England, if their writing is any indication, we might not understand their manner of speaking.
It all had to have changed due to inculturation and the melting pot but doesn't explain your exception.
There is an island in the Chesapeake, Tilghman Island, where they say the English dialect remains much as it was from the first English settlers in the 1656, due to the Island's relative isolation for the first 300 years. The phenomenon has probably faded in my lifetime, tho, due to television.
One of my elderly relatives who was born in Maryland had a very strange accent. When I went on my roots tour in Ireland, where his father had migrated from, I heard that strange accent again, which was quite localized in a small area of two towns, and not at all like the "Bells of St. Mary's" stereotypes used by Hollywood.