As for the difference between the U.S. healthcare system and healthcare systems in other developed countries, if they had the same output of health care services, I would agree, but the US has far more diagnostic equipment per capita and more advanced treatments. It has the best neonatal facilities in the world. These are extremely costly and some of this expenditure doesn't actually produce that big of a difference in outcomes because it's really just dealing with end of life care, or a relatively small number of patients (e.g. premature infants). But when people are free to spend their money as they wish, this is what they prioritize. I'm also not ruling out that the U.S. healthcare system has less efficient government intervention than the healthcare systems of other developed countries. This is not mutually exclusive with the idea that, more broadly speaking, the structural change towards more government intervention has raised costs across developed world healthcare systems.
The more important question in my opinion is why health care spending across the entire developed world has skyrocketed over the last 40 years. It can be fairly inferred that the cost increase is directly related to increased administration and a lack of the kind of cost-cutting innovation seen in every industry that is substantially more market-based / consumer-driven, i.e. less top-down regimented, than healthcare.
Even cosmetic and laser eye surgery has seen costs come down over the last 40 years. That's what we should be seeing in the rest of the healthcare industry. And the reason we're not is because they operate under very different economic forces than cosmetic and laser eye surgeries, on account of government encouraging people to be covered by either public insurance or private insurance.