In each case you’re responsible for paying for your own medical treatment, subject to the following:
1. The very, very poor qualify for subsidized medical care through the Medicaid program.
2. People 65 and over qualify for subsidized health care through the Medicare program.
3. Private medical insurance is available the help cover the insured’s obligation to pay (subject to being able to pay for it), but the scope of coverage largely varies from plan to plan.
Fault only really comes into play in connection with the right to sue the party allegedly at fault for damages to cover medical care.
This is highly, highly, highly simplified, but it gives you the flavor of the fucked-up-ed-ness of the system.