Not everyone in the US has health insurance or (more importantly) the same quality of health insurance. Insurers here have the final say on whether they'll cover certain treatments, medicines, procedures, doctors, practices, etc. as well as how much they'll cover, how much they'll charge the patient, or how much any use of the insurance will affect the price of said insurance going forward. Insurance often prefers you work with doctors, practices, facilities, etc. within their own list of approved doctors, practices, etc. and going outside of that list for any reason may cause you to have to pay for any goods or services out of pocket. Then lastly you have to remember that both health insurance as well as hospitals and clinics are generally for profit businesses trying to maximize profit and minimize costs.

And the little cherry on top of the whole situation is we're in a political landscape where even having universal access to healthcare is labeled as communist/socialist by many in a derogatory way.