The US currently ranks 56th internationally when it comes to infant mortality. We're doing worse than just about every other rich country: the US has 6.17 infant deaths per 100,000, compared to 3.36 in Finland and 4.16 in Austria. A bunch of non-rich countries — like Cuba, Bosnia, and Serbia — are beating us too. Explanations for this vary*, but a recent working paper by USC's Alice Chen, MIT's Heidi Williams, and University of Chicago's Emily Oster notes that there isn't a gap at all for rich, white babies.
The difference is that disadvantaged babies die at a significantly higher rate in the US than in rich European countries. America's excess infant deaths are almost entirely a product of our level of inequality, and low-quality health care for the poor.
The authors find that there's very little difference between the US, Finland, and Austria when it comes to deaths in the first month ("neonatal deaths"). The differences come when you look at months two through twelve of an infant's first year ("postneonatal deaths"). Then, the authors break down the mortality rates for each country by social standing. American children of rich white moms who went to college do just as well as their Finnish counterparts, but there's a big mortality gap between less advantaged groups in each country. "Higher postneonatal mortality in the US," the authors write, "is due entirely, or almost entirely, to high mortality among less advantaged groups":
"This postneonatal mortality disadvantage," they conclude, "is driven almost exclusively by excess inequality in the US."
The paper isn't primarily concerned with how to fix this problem, but the authors do note one promising option: home visits by nurses. "Both Finland and Austria, along with much of the rest of Europe, have policies which bring nurses or other health professionals to visit parents and infants at home," they note. Randomized trials in the United States have found similar programs reduce child abuse, neglect, and injury, though effects on mortality are less well-established.
* They include differences in reporting extreme preterm births (which some countries classify as births, raising their mortality numbers, and others classify as stillbirths, lowering theirs), differences in birth weight and other health indicators at birth, and differences in care after birth. One methodological advantage of the Chen, Williams, and Oster paper is that the countries it compares — the US, Finland, and Austria — use the same reporting standards for preterm births, eliminating that potential source of error.