In the U.S., insurers cannot be prosecuted for anti-trust violations under McCarran-Ferguson. care providers and suppliers tend to engage in anti-competitive practices, and the state does not provide price controls.

Also, EMTALA prevents hospitals from denying treatment for ER visits. People without insurance use these frequently as they have no other alternatives for care. ER visits are incredibly expensive and its a partial reason for price spikes.

Basically the US healthcare system is a patchwork of system tied to employment (which stemmed from wage controls during WW2). No one's been able to rework the system since there are too many entrenched players making too much money