I am a U.S. citizen. Yes, cost is a huge issue. We would not have to rip out private insurance, but we would probably have to regulate pricing, which is how it works in Germany. Folks should be welcome to buy supplemental insurance as they do with Medicare. There's basically four models[1] for providing health care, and the US has all of them:
The Bismarck model like Germany with multiple payers, but they are non-profit and pricing is regulated. Doctors and hospitals are private, and there is still supplemental private insurance. Financing is a combination of employer and taxes, where the government takes over the employer portion if the person is unemployed. This is sorta what the U.S. has for those with employer subsidized health care except for the insurers being for-profit and unregulated pricing.
The Beveridge model like in the U.K. financed through taxes and where the government provides care. This is so-called socialized medicine. In the U.S. we have this system for veterans in the form of the V.A.
The national health insurance model, with private doctors and hospitals but the government is a single-payer. Canada. Medicare.
And lastly, out-of-pocket.
We use all of these in the U.S. and it's insane.
We could in theory adopt a Bismarck system. Force the insurers to be non-profit. Make everyone work off Medicare pricing. Supposedly existing Medicare pricing is too low. Fine, let the doctors and hospitals negotiate that with Medicare. Allow supplemental insurance for those who want it.
MFA polls badly when you ask Americans what if they had to give up their current insurance. But I think this is misleading. Of course it's going to poll poorly if you ask someone to give something up. That's basic loss aversion. Turn the question on its head and ask a bunch of 65+ year olds how they'd feel about giving up Medicare in return for their Medicare withholdings back to buy their own private insurance. Guessing that wouldn't poll too well.
I don't think MFA is necessarily the best option. Americans value choice. But it seems to be the universal care option with the most political momentum right now. I'll take it. But I'd be happy with a Bismarck-type system too.
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596027/