Did you know that 2.5 millilon employees work in healthcare insurance and that a single payer option would probably reduce that in a huge way, creating a massive group of unemployed people? There are dozens of major insurance companies who, in the course of daily business operations, duplicate the work that is being done at competing companies. Obviously, Blue Cross' accounting department isn't going to do the accounting for Cigna, and so you get two accountants doind the same parallel work multiplied across all the companies. But if the US Gov't is going to do all the work in a single payer system, you'll have a massive cut in employment. No way around it. I don't think people realize that the sudden disappearance of probably 1.5 million jobs will be a reality in that case. Esepcially not Trump who has advocated for single payer and ran on a major employment focus.
FWIW, even countries with fully socialized medicine have their own private healthcare insurance industries (ex: UK). But even so, this strikes me as a backwards argument: health insurance is too expensive, so we should preserve the inefficiencies and bloat already present in the system.
So far, the clearest summary of the ACA's shortcomings has been that it addressed health insurance coverage without doing enough to address costs. So now you have fewer uninsured people waiting until the last minute to get treatment instead of preventative care, and fewer insured people being denied the coverage the payed for due to undisclosed domestic violence. But the drugs, the scans, and the doctor salaries are still roughly the same. And medicare still can't negotiate drug prices.
So the delta flow of money is still heavy in the direction of providers.