No argument here that the jobs are more lucrative, on paper, South of the border. Just trying to point out that there are lots of aspects to consider when you're looking at compensation. Being young, healthy, and single in the US can net you a lot, but I suspect that other bills would quickly eat up the difference if you aren't all 3 of those things.
As a Canadian who moved south for work and is rapidly approaching or in middle age, this is my position on the healthcare here: If you have good insurance, it is AMAZING! I understand that others have it worse, but all major software dev employers that I've looked at had really really great HI. In Canada OTOH, the service is much worse for non-emergency things, but everyone gets to have it. From an ethical standpoint, of course I support some kind of 'everyone gets sensible healthcare'. But I pay less out of pocket here than I would in Canada for my family of 5. Financially, moving back to Canada would be a disaster.
The Canadian and US labor markets are pretty interconnected so in my opinion these companies are going to have to start raising salaries if they really want to get talent. I feel like I read something on HN every week bemoaning the Canadian tech industry, when most of the problems have a pretty simple solution: pay more. Of course, that's easy to say but not necessarily easy to do financially.