As far as I recollect discussing this before one will actually save younger children in most of Nordic countries e.g. than in the US, and infant mortality rate is still much lower.
There are several reasons the US rate is so much higher than in other developed countries. The US does not have universal health care, which means large sections of the US population does not get adequate follow up during pregnancy.
If you look at health care for the poor in the US, it is generally geared towards emergency care. They will stitch you up if you are about to die. However it generally does not cover regular doctor visits and checkups. Hence in the US a lot of expensive effort goes into saving babies when born, when the problem could far more easily have been resolved early in the pregnancy with better checkups.
The US system is simply not very geared towards simple preventative care. Where other health care systems tend to focus on simple cheap system. American health care is overly focused on advance equipment, complicated procedures and basically anything which gives a lot of prestige or profits.
Problem is that such a health care system does not perform very well in the real world. You end up with very high costs and poor results.
E.g. a lot of health problems in the US is actually caused by over-treatment. That is the irony of the US system. Poor people who need help don't get it. People with expensive health care plans OTOH are subject to invasive procedures they don't need because it brings in profit. E.g. the US has overuse of surgery. So basically people who don't need surgery are cut open in the US. And that does take a toll on your health.
The opioid crisis killing Americans is a variation of this. Basically it is overmedication for the sake of profits. The health care system is actually a contributor to the bad health problems in the US.
It really should lead people to question for-profit health care, but it seems impossible to question anything about capitalism in the US. You speak to deaf ears.