Not sure if you are trolling but are you alluding that the US population has healthier teeth? The "difference you see" is most likely just the much more widespread usage of bleaching in the US (which actually worsens the health of your teeth).
I have no idea if there is a genetic difference in the US, but according to Wikipedia, it seems modern toothpaste first took hold in America.
Colgate, a US company, introduced modern toothpaste in 1873. Later, toothpaste that had been developed by researchers in the UK and US, did not find commercial success in the UK, and they focused on the US where it took off.
This suggests that the US were more interested in the appearance of their teeth.
https://en.wikipedia.org/wiki/Toothpaste#:~:text=Pre%2Dmixed....
This links to OECDs compilation of WHOs data, was easier to get the overview from imo: https://www.oecd-ilibrary.org/docserver/health_glance-2009-1...
Having lived in both the US and France, I can say that it’s been my experience that Americans have “nicer” looking teeth. Whether that translates into anything medically relevant is apparently really difficult to prove.
I’m sorry I didn’t dig any deeper than the link that was presented but it was about adolescent kids. And no one is saying that these differences show up in young people.
When I lived in Canada (which I assume isn't too different from the US) with poor social security due to my legal status, I never went to a dentist because it was far, far too expensive.