Good news is that most of the Canadian population lives within driving distance of US cities.
Other side of that coin, though, is that if 50% of the Canadian population is in "the red triangle" ....

... how do you deal with the 50% of people who don't even live within reasonable driving distance from a provincial capital, much less a U.S. city? Where I live in northern Ontario, it's a 15-17 hour drive to Toronto, and about an 8-ish hour drive to Winnipeg or Minneapolis (closest decent-sized city in the U.S.). If I go to one of these spots for medical treatment, I get some but not all of my travel $ back and I have to front it before I can even apply. Not everyone can do that. Short of moving everyone to Toronto, Montreal, Vancouver, Edmonton and Calgary, gotta figure out how to deal with the other 50% when it comes to health care above a certain level of complexity.
Also, don't discount "centre vs. periphery" issues. We have a cancer centre here, and a while back (Team Blue happened to be @ the helm, but as others have said, more than enough issues/stories for both main parties to get the blame over time). Under the old regime, if I went to Ottawa for treatment, I would get a fraction of my travel costs back. When the backlog at the Ottawa cancer centre got too long, patients there would come to the cancer centre here for treatment because the backlog was WAAAAAAAAY less. Guess how much of their travel costs were covered? 100%. Needless to say, we in the periphery were not impressed.
Apologies for the health rant ....