However, this isn't really the top problem on the list. It definitely is one of the last items, if not the last.
Allow me to make a simple, yet imperfect, parallel.
If you buy a Toyota your auto insurance will cost X.
If, on the other hand, you buy a Ferrari, it will cost many times more than X.
Why?
Because a Ferrari costs more to repair and the probability of accidents might be statistically higher given the extra power, etc.
Insurance costs are a result of statistical analysis of the underlying probability distribution of costs to the insurance company based on a range of factors. These would include known and unknown costs, personal history, regional factors, legislation and more.
One cannot magically reduce the cost of insurance and obtain better results on the other end. You cannot force insurance to cover the potential costs of a Ferrari to only cost as much as it does for a Toyota. You can only do that if you remove coverage. For example, you are not covered if the car is stolen, damage or if you are driving above the speed limit and you are required to install a monitoring device in the car. In other words, make the potential cost surface as equivalent as that of a Toyota.
This is why the US does not have an insurance problem and our healthcare system will never be fixed through insurance. This "Medicare for All" nonsense is exactly that. It's like forcing Ferrari insurance down to Toyota level. In other words, it turns a blind eye to the underlying structural issues in the system, fixes nothing and pretends it is a solution.
Lower insurance costs in the US is a theoretically simple task that, in practice, is difficult due to our politics. We have to reduce costs. And these costs are related to the regulatory burden, the financial reality of lawsuits and the cost of medical education, to name three factors.
When you are rolled into an operating room in the US and are surrounded by, say, ten professionals, their collective school loan debt is likely in the two to three million dollar range. They each spend tens of thousands of dollars a year in insurance to protect from lawsuits. Each of the pieces of equipment in that room, from the masks to the ventilators, endoscopes, scalpels, table and more are the result of having spent from millions to billions of dollars in regulatory licensing and testing. Each of the companies making these products must maintain teams of attorneys, entire floors full of them in some cases, to protect against lawsuits. They must also pay for insurance for the same reason. The hospital in which this operating room exists is also the subject of pretty intense regulations that start with the planning and construction of the building and the rooms. The permits alone to build a hospital can cost a hundred million dollars and take ten years to obtain. Once built, the hospital is subject to yet another layer of cost-increasing regulations (the current example of not being able to use industrial N95 masks is relevant here) and must carry insurance to protect itself an its entire staff from lawsuits (which could cost billions of dollars).
That is a super simplified view in to the innards of the US healthcare system. None of these costs and problems are magically fixed by changing insurance, no matter what we do. We can take it away from employers. Sure. So what? How does it change any of the above? We can make it this crazy "Medicare for All". So what? How does it change the realities I disclosed above?
No, insurance isn't our problem. Sure, it could be better. Yet it is pointless to even talk about making insurance changes when the underlying cost structure is massively broken.
I hope this clarifies things for you. I understand it isn't easy to understand the inner workings of something like this from afar. I only understand the way things are in other countries because I have lived elsewhere, otherwise it would be hard to grok the differences.