I asked AI to put together a list of all the OECD countries, the year they established their system, and the relative size of the health care sector at the time.

Great list. Your only reason that the U.S. can't do what those 30 countries did is, essentially, that the U.S. system is too big and entrenched to change. Yet all those countries did it in recent historic memory. Rather than focusing on the prior size of the expenditures relative to GDP, it would be instructive to look at whet they did. There are thirty different ideas there about how to provide UHC. Some better, some worse. A lot to learn from, a lot of possibilities to come up with a workable system.

As one example, I know a little about the system in Israel. Prior to the 1990s there was no UHC. Most people were enrolled in HMOs voluntarily, or through their trade unions or government employment. Some people were left out. Now the law requires every person to be enrolled in one of four government authorized HMOs, all of which existed before the law. So essentially the system hasn't changed much. It has only been enhanced to cover everyone. The funding flow has changed. The government funds the HMOs mostly through a "health tax" which is a payroll tax, and supplements the funding out of the regular budget, funded from ordinary personal and corporate income taxes. Individuals have the option of privately buying an enhanced level of coverage from their HMO. They can also pay health care providers privately, which is a bit odd because you can see the same doctor or clinic or hospital through your HMO or as "private pay".

So that's one system. Every country has its own quirks. I have no doubt that the U.S. can develop its own system to make sure everyone gets adequate health care, and save a ton of money doing so. There will be some winners and some losers at the margins. So what?