I think you have to plan carefully and do a lot of research if you want to go that route.
For example, typically you can't have access to another country's free or subsidized healthcare system unless you're a citizen or permanent resident. Obtaining that status can take years. In Canada, for example, you have to apply for permanent resident status from outside the country, and the process is pretty rigorous. It can take two to five years to get permanent resident status here. And then you're faced with a healthcare system that's underfunded and understaffed (at least that's the current situation in many parts of Canada) with the result that actually getting healthcare can be a challenge. My girlfriend had to wait three months just to get a routine x-ray, and had to wait six months to see a specialist. It's almost impossible to get a family doctor in Montreal (most of the docs in town stopped accepting new patients more than a decade ago); if you get sick you either go to a clinic or the emergency room. You never see the same doctor twice. Hopefully this situation will be resolved eventually, but right now it's a bit of a mess. (I realize that not all Canadians have had bad experiences like this, but in Quebec it's a real crisis)
The other issue is that your taxes become more complicated when you move overseas. I used to do my own taxes but had to hire an accountant when I moved here from the States...I have to file in both the US and Canada (although I only actually pay taxes to Canada).
So if you wanted to do this, you could (theoretically) begin the process in the US before you are ready to retire. That's actually better than having to be there to apply, as you can get your ducks in a row in advance.