That's a straw man argument. Nobody says it's trivially simple. Everyone acknowledges that it's difficult and complicated.

I don't think that's true.

Oh, sure, everyone acknowledges that there are in fact a lot of moving parts to setting up a big national health care system. That part is acknowledged to be difficult and complicated. But the politics of it, and the balance of interests of it, are usually framed as being trivially simple. Either the typical "everyone else has this system so it has to be doable," or the assumption that since we're spending $X on health care today it must be possible to set up a UHC system with just spending $X on it.

You almost never see any discussion of what we're talking about on this thread. That there are a lot of interests other than insurance companies that will inevitably be hurt by any transition away from the status quo that results in materially less money going to health care.

That gets handwaved away by a simplifying assumption that the administrative savings will more than make up for it. Again, because everyone else is doing it. But that completely overlooks the fact that the biggest single obstacle to cutting health care spending in the US down to global levels isn't insurance companies, but all the people who are currently getting all that health care spending. The medical providers, the hospitals, the elderly retired, the union workers, etc.

There are a ton of people who would be net losers if you transplanted a European health care system here into the US. That's the main political obstacle. And I think it gets dismissed as trivial - or generally wished away as nonexistent, erased by the magic of administrative cost reductions and the obvious feasibility of examples in Europe.