This is definitely not the case, the standard of care available to poor people roughly matches that of the region where they live, it is just typically less convenient and more ad hoc. Been there, done that. The details vary with locale but healthcare is generally available to the poor at little or no cost everywhere in the US. It is a different experience than an insured middle class person but outcomes are largely the same at a given facility.

I've personally seen a (likely illegal) migrant worker helicoptered to Stanford hospital where they surgically re-attached a severed limb. Best standard of care available, far above what was required, with no possibility of repayment.