US Medicare insurance is good only in the US and not overseas. If we were to become ex-pats, Medicare would be useless despite that fact that we have paid for it during our working careers. There would be no interest on the part of the US government of paying our insurance bills when we are on travel and we make sure to always take out additional health insurance to cover any emergency. It's not optimal but it's the reality.
As it stands, the UK health service has a reciprocal arrangement with the fellow member countries of the EU; people (British) going to member countries on a non-residential basis need only apply for, and carry, a card (E 111?) that entitles them to the services. My daughter has had to use hers frequently because of ear problems that seem to manifest themselves with swimming pools, and her younger daughter, the doc, ended up in the local hospital with some deep pains when she was just a kid: even then she showed more interest in the procedures than in her problem, which was resolved.
Anyone from the UK going to the States has to carry a distinct, expensive insurance policy; I recall that from our couple of shoots in Florida. I always wondered why a relatively prosperous country like yours didn't appear to have an all-included, cradle-to-grave health insurance plan for its citizens too, free at point of delivery, but contributed to during working life via taxation and obligatory national subscription via pay packet. As with the EU countries, it need have absolutely no bearing on the ability to take out separate private medical insurance for those with pockets that stretch that comfortably. Feels like a basic human consideration that is independent of all other aspects of life. Listening, as I do, to a lot of Louisiana radio, I'm always a bit surprised hearing commercials that tell people their children may be considered in some health insurance if they, the parents, earn in a particular financial bracket. To my ears, it sounds all wrong. But that's just me.
Many in Spain have both forms of insurance, especially when the children are young, because it can save on waiting times. The same doctors often appear, from my personal experience, to work in both services: the nationally provided one as well as the private.
If I were rich, one thing I would do is provide something for the cancer department of our local regional public hospital. Obviously, I mean
rich!