In the UK you can choose to purchase private health insurance on top of the state provided health care if you so wish. A quick search suggests the same is true for Canada.

I don't think "proactively healthy people" is the right dividing line. It's more like "wealthy people". The point of the universal system is to provide a reasonable baseline for everyone. In my experience the UK system does this. Of course it has issues. So does the US system. The real debate is about which tradeoffs are preferable at a society-wide level.