To say it is irrelevant is a bit harsh: despite how dystopic US healthcare stories can be, a lot of people actually live with that system. Those real people can get good use from this study, even if its results can't be easily applied in other parts of the world.

not rly, it is an American study, so it should target Americans, However it is a valid concern/hypothesis that women which give birth younger tend to be of lower health overall due to various socioeconomic conditions.

Ah, but this does not claim to be a study of what age is the optimal for US women to be pregnant in given the current health care system; it supposedly makes a more general claim (or at least, that's what its title says).

anyone with 2 brain cells will deduce what you said no matter the clickbait title.

If it's known, can you not adjust for it?

Just have your country of choice run their own studies.