The US currently spends about $5 trillion on healthcare. About $1T of that goes through Medicare, another $0.9T through Medicaid, which leaves about $3T. Non-government spending is $1.6T through private insurance, $0.6T out of pocket, and $0.5T charities.

The "universal healthcare would be cheaper argument," which I believe, is based on shifting that $3T of private payments into government spending and bringing the ~85% efficiency of care by private insurers up to the 98% that Medicare claims. i.e.: eliminating roughly $400 B of insurance company profit. That still requires $2.5T revenue increase, which is about 50% of current revenue.