However, that isn't enough. US healthcare is wildly inefficient because the paying customer is different than the serves customer. This has been known for sixty years, since Arrow published his paper (he identified four reasons, three of which are not exclusive to healthcare and seem to be mitigated well in other industries). I'm surprised people posting can't quite see this: when you go to the doctor, would you call the experience efficient? You check in, then wait, then are called back, tell the nurse or PA why you're there, wait, see the provider who asks you again why you're there, has a short exam, wait, finally get all the paperwork and sign out.
If you have labs or tests, you then wait again. And of course if you need a specialist, you wait again, sometimes for months. If you need any sort of "specialty" medication or equipment, then you REALLY wait, as specialty pharmacies, DMEs and the like jump in.
The whole system is woefully inefficient, and overhead is only a part of the explanation. No one knows what anything costs, and the people who pay (insurance providers, the largest of which is the US Government) want to believe they're not getting scammed - they still are, but at an acceptable level.
The question we ought to ask is how we can buy better health outcomes for people. And I think part of the answer is that in most cases, individuals and families themselves must allocate resources they control to make this happen.