I'm a median to upper-middle American, and I get great value from my healthcare. It's not obvious to me that a system that raises the experience for mean, or even the bottom end, of the distribution would be a good thing for me in many respects: emergency wait time, access to top percentile specialists, out of pocket costs, just to name a few. It also seems to me that you neglect to factor in that people of means, the world over, come to the US to access care from world leading treatments in many conditions. So they might not want American care in their country, but plenty surely want it for their own bodies.
Put simply: your "good effect" often smuggles in assumptions about which part of the curve to treat, and implicitly undervalues degradation of the status quo for others. You, as is the habit of liberals, would like to have a debate wherein your moral values about who deserves what and who should be deprived, is taken for granted. I'm sorry, it's not immediately obvious to me that a system where 10,000 people wait 6-12 months for lifesaving operations is better than one where 1,000 people can get the operation in a month and the other 9,000 might have to go into debt to do the same.