If only the United States had some kind of system of geographic administrative divisions similar to the countries that make up Europe...

Right, and states are free to enact single-payer/universal health care for their residents if they so wish. In fact, you might want to look at the Massachusetts health care system.

But implementation at a state level is obviously not what this thread is about.

For a US-wide health care system you need US-wide infrastructure/bureaucracy. This decreases efficiency.

I'm down with this -- this is how Canada's system is run. Each province provides insurance for its residents meeting the requirement to provide a socalized system as defined in the Canada Health Act. States should provide the socialized system, the federal government should mandate a public option exists (either single payer or two-tier) and the basic rules that govern one.

That completely goes against the idea of economies of scale. If smaller organizations were inherently more efficient, mom-and-pop stores would be beating Walmart and people running online stores out of their garage would be beating Amazon.

"Economies of scale" isn't a universal idea that you can apply to literally any industry/sector.

Unfortunately, medicine is not retail. Otherwise are lives would be a lot simpler. Would it be more efficient to introduce Amazon-like policies to medicine. For sure. But unlike Amazon fulfillment centres, you can't just close all the hospitals in a city and build a mega hospital 1 hour outside the city and expect anyone to go along with that.

Pretty much everything that can be "economically scaled" in the medical industry already has been -- the drugs you are receiving to treat X condition in NY and WA are probably going to be from the same company. The MR machines you use in TX are the same brand as the ones used in PA. This means those things are cheaper than they would be if they were being produced by "mom and pop" shops. Economies of scale are already in play. It's all about fixed vs. variable costs.

My point was about admin. When the scale of an organization goes up, the admin costs go up, not proportionally to the value that this admin provides. It's necessary if you want to get bigger, but not proportionally useful. With a national health system, the number of doctors you need will not go down. The number of imaging devices you need will not go down. But the amount of centralized bureaucracy you need WILL go up.