The USA is probably more split along rural vs urban divisions from what the elections say. Up here we have much stronger regional identity. East coast, Quebec, Ontario, Prairie and B.C all have pretty distinct cultural frameworks. There is some Urban v Rural, but that really is everyone hates Toronto more than anything.
There is a strong Urban vs Rural aspect to the situation in Canada from what I can tell.
But yes, the US regional situation these days is less of a thing than it is in Canada.
The thing is a Regional party in the USA that managed to take say 40 seats on the House and 4 in the Senate could become a very real power broker on some issues, even in the sense that it would cause the two majors to have to work together more to blunt them. And reduce the threat of further erosion of their duopoly.
The problem is that none of the current main "third parties" are remotely interested in doing this work.
They just pop up for the Presidential elections.
A regional party in the US
is viable at the Congressional level.
We had the Populists in the late 1800s, then the Progressives, then Farmer-Labor.
As always, they weren't
solely regional in focus, having real large scale national ideas, but they had a regional base of power that got them representation.
It isn't an impossible approach.
Unfortunately, the most consistent group to do something regional across a few states and with a consistent ideology is the South. You can still see those voting patterns show up.
But there are other areas that might have some kind of consistent view that could pull out of one of the main parties.
I don't think it could ever be a truly regional for regional sake party outside of the South, though.
Otherwise it would need to have a national policy view shaped by a region.
Water rights management across the Southwest could be something.
A cultural position of note (a blob with a specific view on abortion, for instance) might work.
Some kind of monetary policy that affects one region in a specific way.
I could see a border party with a view on immigration that was consistent across an area acting as a lynch pin.
We just aren't seeing anything like that out of the current minor parties, which focus on the presidency instead.