I don't think that's a reasonable criticism of Medicare. Most other countries with universal healthcare do require you to be in the country to get that care. Europeans don't get much benefit from their universal healthcare when they leave Europe for example.
The EU is not a nation state, yet roaming in Europe between nation states they get universal healthcare. As do visitors from treaty nations outside the EU.
There are no good bilateral health treaties with the USA For a reason. As an Australian, I have private health cover for longterm services like physio, optical and dental services. For life threatening emergencies I go public and can do so in bilateral treaty countries.
That's how I understand the problem. Happy to be corrected.
I had Medicare on a temporary visa in Australia and had to go to the ER. I don’t think I ever got any bill at all. It was really amazing all the way around.
The contrast made me feel ashamed to be an American, to be honest. I grew up in poverty, and have internalized not going to the doctor for any reason besides an actual, literal life threatening emergency. My folks were volunteer firefighters and first responders, as we lived in an isolated rural area on dirt roads, so we were the closest emergency services, now that I think of it.
I’m back in USA now, and I still have to live that way, as I’m unemployed and trying to start a business. I have no assets and am nearly homeless. It’s no American Dream for everyone.
I wrote a bit about my Australian medical emergency here:
My healthscare is an admittedly unusual one, but it applies globally - with a single country exempt. I can get treatment in Sri Lanka, Greece, Moldavia, North Korea, Ghana or Iran and they will cover it. But not the US as ithat system is the most broken and most expensive in the world.