Earlier quoted context omitted.
> companies are immensely profitable That's not necessarily true. If all the for profit insurance companies reduced their profit margins prices wouldn't go down that significantly. I think it's mainly the extreme inefficiency and much higher labor costs.
> extreme inefficiency and much higher labor costs Which is mooted with single payer. Roughly 1/3rd of costs eliminated. Last time I checked (mid 2000s). Probably more now.
As in doctors, nurses, and other personnel will accept lower salaries because they won't have any choice? I'm not sure that would work in the US.
Also, there are relatively efficient non-single-payer systems in Europe (e.g., IIRC, Switzerland and the Netherlands don't have the equivalents of Medicare/Medicaid). Proper regulation, including price transparency and regulation, would solve most of the main issues and would probably be much easier to achieve than a single-payer system.
A federally imposed universal single-payer system seems to be totally politically infeasible. The best you could hope for is a two-tier system with the government continuing to subsidize for-profit healthcare (including insurance) companies (all extremely expensive treatments covered by the government, but most people who can afford it will continue having private coverage as well).
Wouldn't it be much easier (and possibly more efficient and equitable) to just adopt the Dutch system?