What's the root cause of this sorry state of affairs?
I don't think there is 1 reason why the health care system is so bad in the USA. If I had to pick the most important reason it is the legal infrastructure. The system is designed (with legal constraints) to favor entrenched interests instead of customers and stakeholders.
It is true other rich countries also have massive room for improvement. But the USA stands far below all other rich countries. The costs in the USA are about double the average rich country. And the heath care outcomes are mediocre. And the economic and personal outcomes are extremely bad. Tying health insurance to an employer is an extremely bad idea - that is rare among rich countries (I am not sure if the USA is unique in this bad practice, or not).
I have many posts on the problems on USA health care and how to improve the health care system in the USA.
It is possible to try and find the common reasons for health care failures in the USA and other rich countries but the USA is really in its own class of badness.
Related: Can We Expect the Health Care System in the USA to Become Less Damaging to the Economy? - USA Spends Record $2.5 Trillion, $8,086 per person 17.6% of GDP on Health Care in 2009