1. Well Sanders himself uses the Socialism word. But surely you cannot accept that the criticism you aimed at socialism will all apply to a "Sanders-World", but not to a traditional republican US.
2. Seems strange that this mental group behaviour should dissipate at the 5-10m population mark to me. I don't think it's right to say that the Scandinavian countries have been outperforming the rest of western Europe for centuries. In fact I'm almost certain it's not.
3. That's part of it, but only part of it. The fact remains that in a capitalist health care system profit margins at each level will also drive up costs. It might be that this is offset by the market forces driving cost down, but this could also come at a cost to the actual health care being provided. I don't think you can look at the current situation in the US compared to more socialists countries worth comparing them to and say that the US system is superior based on cost. Inject another 40% on top of the NHS budget and I think you'd see improvement. The US health care system is also famously polarized in it's services. Sure you'd get good treatment, but that's not the situation for every citizen - or even the majority. If providing good health care to those who can afford it is the only goal it works, but for me that's not enough.
4. I remember listening to that episode of Freakonomics too
I think there's almost certainly a directional problem. But only to an extent. And IIRC that's the point that was being made too in that podcast...
I think money plays a massive role in it and it's quite literally destroying the concept of democracy and turning the country into a plutocracy of sorts. It's not the done deal yet, but the trend is pretty clear.