Hello OP,
I am living quebec, I am canadian myself.
In my point of view, here are listed major differences between USA and Canada
Politic : USA is a republic while Canada is still ruled by parliaments. Which makes a bit different the way laws applies from a province to another compared to how a state can have theirs.
Health : As you mentionned, Canada has free health system, that's one major difference and what makes many americans JEALOUS of Canada. But, I must say, this system does fail. Public Hospitals are always overloaded and you can barely get to have your own doctor within 5 years. Going for an emergency may take up to 12 hours as well. Paid services are way better. At last, quality is, I believe, as good as it is in USA. (What I mean here, is that I wouldn't trust an american doctor not speaking english [[america does include mexico]])
Justice : USA are not laughing with justice. You should be scared to commit a crime in USA. While in Canada you know what you will receive for punishment will be ridiculous. While USA appear to be ready to start unwearing peoples in airports, canada are more respectful of each one's privacy and got their laws softer.
Quebec : Canada is involved in language debate. You will have to deal between french and english if you pick Montreal.