What difference does it make if you pay health insurance premiums or a slightly lower amount of tax on average for similar public coverage (since profit motive has been removed)? If anything, if most people were on the same public coverage, their choice of physicians would increase, since most doctors would have to accept the “default” coverage.
Someone else’s money? Plenty of money to be cut from bloated defense budgets, welfare to defense contractors, subsidies to rich countries that don’t need them (Israel, Saudi), and from the costs of running a predatory “justice” system that incarcerates almost 1% of adult residents of the US.