With choices of two major political parties, US voters have do not have granularity to approve or disapprove long term/chronic/fringe issues or issues that disproportionately affect a small minority of the population.
I'm not sure it's a deeper structural issue. The issue is actually pretty simple; first-past-the-post voting. This automatically leads to a two-party system.
Canada currently has 338 MPs and over 80% (!) of those (278) belong to one of two majority parties.
So yes, in theory Canada has a multi party system. In practice this multi party system is severely damaged by the effects of the FPTP voting system.
There are mathematical reasons for FPTP to result in two party systems. [0] explains it pretty well. There don't have to be deeper underlying stuctural reasons for the dichotomy.
So to combat two party systems, replacing FPTP with an alternative voting system seems a pretty reasonable step.
Which is also true of Australia which has had instant runoff voting for nearly a century.
I would suggest you look at the actual examples in the wild, and see if they have FPTP (or party proportional representation, which is essentially FPTP with all the same spoiler effects), and which don't, and see if they match your expectations to any degree better than random chance.
You can prove just about anything in "math" in a vacuum. The recent push for FPTP really strikes me as the kind of wonk stuff that people bend themselves around as a huge fix, when the reality is it empirically doesn't do what people thinks it should do, and comes with it's own problems. It's a lot of wasted political capital for very little if no benefit.
This is a problem. That being said, several major states have a good amount of direct democracy, including allowing for state constitutional changes, and there are often more than two viable candidates regardless of the letter after their name. I think this is a plausible way out of the two-party two-ideology stronghold that incites further polarization. Where I vote, between these two factors I don't usually think about a party because there may be 4-6 different candidates with relatively different platforms listed under two parties, and 10-20 referenda listed under that with no party.
It the case of the U.S., nobody is to blame but the U.S. voters.