Sure. However, the voters still decide. And they elect people who are -for the most part- hostile to changing the insurance-paid medical system. Heck, Obama didn't really change it (i.e. it's still an insurance-based system), and it still barely passed (and was one senate vote away from being scrapped a few years ago).

But that's because they don't want to pay for it. It would be insanely expensive to provide universal single-payer health care at the current prevailing price for medical treatment. We don't pay more for health care than other Western developed countries because of insurance costs. We pay more for health care than other Western developed countries because we pay more for health care.

That's why no state has been able to do it, even very liberal ones where the voters strongly support single-payer systems in theory. You can't switch to single payer universal health care unless you slash what you pay providers for their services. And no one's willing to do that.

Europeans, Japanese, and others, have all figured it out.

No, they didn't. That's the "path dependence" part. They never had to do what we would need to do. They never had to make a switch. They never let their health care industries grow to be 10% or more of their economies - or have 10% or more of their workforce be in the health care sector - and they never let their medical service providers raise their rates to the kind of levels we have here in the first place. Once you've got a system where so many people would have to be economically hurt in order to balance the books in a switch, it becomes politically hard to make the switch.

We can't provide health care to all the people who currently don't have access to health care without either: i) paying a lot more for health care at current rates; or ii) cutting current rates. Both choices would be pretty unpopular. The ACA did the former - the federal government basically just paid for an extra 20 million people's health care costs at roughly going rates. That's why our health care costs haven't moved any closer to those of other countries, even though we have fewer uninsured than previously.