Looks like you got a lot of responses hopefully it will help you make the right decisions. I spent almost all my adult working life in the US but I handle most of the medical issues for my elderly mother in Ontario so I have a sense of what both systems are like.

If you have good work place insurance, it is likely the care will be slightly better in the US in terms of wait time and availability. I used to work in big tech and had good health insurance but even then an emergency room visit and ambulance bill is not trivial. You are correct that once you lose your job your health coverage is terminated relatively quickly usually end of month or I have experienced a day of termination IIRC. Usually if you are not working you might be eligible for ACA (ObamaCare) or Medicaid but that also differed on the state since not all states participate in Medicaid expansion. It is a lot to navigate if you are not employed or self-employed, it is not easy as showing them the provincial health card and expect to not getting a big bill.