This is false. There's EMTALA, which requires that emergency services will be provided until a patient can be transferred. But doctors absolutely refuse to provide services based on ability to pay all the time.
https://casetext.com/case/diaz-v-division-of-soc-servs-1, as an example, involved a case where chemo was warranted for emergency treatment, but not on an ongoing basis. The court found they could treat enough to stabilize, then discharge, even if that guaranteed an emergent return later on.
There's a good reason Luigi killed the CEO of United Healthcare.
Only in a very specific, narrow set of circumstances.
https://en.wikipedia.org/wiki/Emergency_Medical_Treatment_an...
It only applies to emergency assessment and stabilizing care, and only if the facility accepts Medicare patients.