Minnesotans tend to sound very distinctive from the vast majority of Canadians. While many from Minnesota can be confused for being from Wisconsin (or vice versa) there is no way I would ever confuse such a person from the U.S. Upper Midwest Great Lakes states with being Canadian (unless Canadian from one very limited area). I can tell a typical old school Minnesota or Wisconsin accent quite readily. Except with a few words, most of my Toronto-raised and other Canadian acquaintances sound more like the more educated from Ohio than they do from downstate NY; they even sound distinctive from most all upstate NYers.

The earlier comment that indicated that people who acquire a second accent early on can acquire another accent easier is definitely true from what I've seen. I've got relatives who went from having a heavy Texan accent to having an upstate NY accent to having a very distinctive Minnesota accent, with the latter being mostly picked up in the adult years. Nothing fake about it at all. Interestingly enough, not all members in that family of the same age range and relocation history share the same accent; the ones who moved without changing accents seemed least likely to change accent or adopt regional word choice in the way of the others.