I first came to Canada over 50 years ago. At the time, some Canadians tended towards 'oot' in about and similar words. I can't speak for the Maritimes or Newfoundland, but that pronunciation has disappeared from Toronto west. Quite homogenized now (TV influence?)

As a geologist, I did fieldwork in many parts of Canada and the U. S. It was very interesting, listening to the different accents and word usages. The only place I had trouble understanding what people were saying was in southwestern Indiana, where southern accents (I agree, Leeneia, there are many southern accents) mixed with those of other regions. That was some time ago, and accents there probably have become homogenized as well.
In an old magazine, however, I read an article by an Englishman who had traveled widely in the States. He complained that Americans spoke a common language, with few of the interesting variations found in the British Isles.