I grew up hearing the joke that Canadians speak funny my entire life, but everyone around me has a similar speech pattern as our neighbours to the south; is that due to American media influencing us? Was there a period in time where the majority of Canadians did speak funny?
It is from the movie Strange Brew from 1983. It was a cult classic and played on every stereotype of rural Canada, including the speech. In rural Canada, there is an accent that is similar, as well as in rural Minnesota, North Dakota, and some other like areas.
There is something called "Canadian rising" which describes differences between Canadian English and American.
I can't explain it, but you may find someone who can at r/linguistics.