Max Roser in Our World in Data:
Why do Americans have a lower life expectancy than people in other rich countries, despite paying so much more for health care?
The short summary of what I will discuss below is that Americans suffer higher death rates from smoking, obesity, homicides, opioid overdoses, suicides, road accidents, and infant deaths. In addition to this, deeper poverty and less access to healthcare mean Americans at lower incomes die at a younger age than poor people in other rich countries.
More here.