The US is an outlier compared to other developed countries for this, but comparable to poor countries.

The same is true for its murder rate.

One factor consistent with that both numbers are inversely correlated with availability (in that prompt is important) and quality of medical treatment. The US also has an unusual medical system.

I have no idea how to verify it, but it is a plausible explanation IMO. At least as plausible as other explanations (or possibly in tandem with other factors).