US has a much higher rate of premature birth than the rest of the first world, which is what this comparison is, not third world and developing nations, which also have high levels of premature births.

The high level of premature births is actually an after-effect of many other problems which we have … some of which are due to our high level of social inequality (urban poverty, babies having babies). Also, our life expectancy is worse than Europe *even accounting for social class*. This is “lifestyle” but not “personal responsibility” but rather the stress of living in an unequal society. For example, working long hours leads to sleep deprivation which leads to cancers. Whereas in Europe the 35 hour work week is standard. And so on.

What’s often forgotten is that at the beginning of the 20th century, the US was a developing nation (charitably) and became a developed nation by the mid 20th. Its strength at the period was relative to almost all of the great powers of the 19th century (including Japan) having nigh-obliterated themselves in a cataclysmic war.