The US healthcare system has lots of problems, but the quality of its infant care isn't really one of them. Infant mortality rates are calculated very differently in different countries which accounts for much of the US's "poor" rating. The biggest factor is that the US considers all births, regardless of how premature they are, towards its mortality rate and is aggressive in its treatment of pre-term births. Many other countries don't count early births or babies born with weights below a certain threshold towards their infant mortality rate.