There have been attempts made to correct for these discrepancies. They end up accounting for a large fraction (but not all) of the difference in infant mortality rates, if I recall correctly.
Most of the rest of the effect is that premature births that everyone considers "births" have a higher prevalence in the US (for various reasons, not all of which are clear). Premature births have higher mortality, obviously.
https://uk.reuters.com/article/us-health-infants-mortality/u... is actually trying to look at an apples-to-apples comparison, and a few things jump out at me:
1) Birth defects. I wonder how much of this has to do with differences in abortion availability and again differences in definition of "birth". Many other countries count a child that dies within some number of days after birth from birth defects as a stillbirth, not an infant mortality event.
2) SUID (aka SIDS) is a huge contributor in the US. In the US this is highly concentrated in ehthnic groups that are largely missing in the comparison countries. Why that is is a good question, but makes this comparison less apples-to-apples.
To know where you'd want to be you want to know the outcomes for your specific demographic in the different countries, which is not something that gets reported very much...