Which countries do you consider not to have a nationalized healthcare system, then we can make a comparison?
Note that even in the US, the government covers roughly half of all healthcare expenditure. The UK government covers about 79%.
> 2. "Cost-effective" is an interesting term, because it assumes we agree on what "effective" means. I want choice, innovation, better health outcomes, more convenience, shorter wait times, etc., and I'm willing to pay some premium (but not 4x or something) for them. For these reasons, I don't want want the NHS system here (nor do I think it'd work here), despite it being better for some values of "cost-effectiveness".
Even if you for some reason believe you don't get this with the NHS (meanwhile most people here considers the US system to be terrifying), you have all of that by combining the NHS with private top-up insurance. The average cost of combining NHS and private insurance in the UK is far lower than the average cost of healthcare in the US.
So you can get the benefits that socializing services have in ensuring universal coverage and ensuring nobody drives up overall costs by waiting until things get more expensive to treat, with the ability to pay for whatever extra services you want.
Fewer people go without coverage, and you get cheaper coverage and more choice since you can still pick and choose from private providers but also get a public option if you prefer that.
In fact, because of the ability of the NHS to rent out resources, even privately paying for operations etc. tends to be so much cheaper even at top end London specialists that if you're in the US and need elective care it is worth checking the cost of flying to London, having it done, and staying in a nice hotel while recovering. For a lot of conditions that'll be cheaper.
Personally I find it telling that it is almost impossible to find people holding your positions in places where people have experienced these socialized systems unless they have the money to pay far more for care that is out of reach of most people.
For 3., note that you're referring to PPP adjusted numbers. The UK costs have also increased more the last few years than I realized. Even so, while the PPP adjusted data does not have the UK stand out as much as it used to, the gap between the UK and e.g. the US still illustrates the most important point.
