The idea of an injured patient having to pay at all for an emergency ambulance ride to a hospital should stun any normal human being living in a civilized society.
America doesn’t have the same kind of social cohesion as most countries. We’re a nation of individualists. The general feeling here (rightly or wrongly) is that healthcare costs are largely driven by your choices in life, and Americans don’t want to feel like they’re on the hook for other people’s bad choices.