You are someone who hasn't lived in many of the 50 US states, apparently: there are no state car inspections in most places. Ever. I know it seems amazing to those of us who are accustomed to them.

Maybe not but you can get a fix it ticket from the police.

You seriously expect your car's auto-headlight-dimming feature to be regularly inspected?

No doubt in California this would show up as a trouble item in the OBD-II diagnostic and that would immediately fail its "smog" check.

Actually, you would probably not get away with having failed auto-headlight-dimming because you would annoy a cop going the other way and get a ticket. But features that aren't so obvious will go uninspected in many locations.