The US is to my knowledge far less strict with any emissions, and have very limited emission inspection. Do you have any example of areas where the US are more strict, including inspections that validate the rules?

With regards to diesel vs. gasoline: Where I live, gasoline is 5 times more expensive than it is in the US, so diesel have been favored solely for its efficiency. We consider anything below ~25km/l (or ~60MPG) to be inefficient, and anything below ~20km/l (or ~50MPG) to be terrible, and that has been our standard for close to 20 years. NOX vs. CO2 is always a discussion, but we do our best to burn as little as possible of anything.

We also try to disincentivize owning old cars that are legal by older standards by having taxes on emission technology (e.g. no modern DPF), as well as fuel efficiency.

(Not that I'm fossil-fuel apologetic—I'm going to get an EV as soon as its affordable. Cars are pricey here.)

That's a difference in priority between particulate emissions and CO2 emissions, right? With one favoring a relative reduction in soot and the other favoring a relative reduction in CO2. That's my understanding anyway, I'm not a car guy.

Not soot. Nitrogen oxides (NOx). Soot is easily taken care of and tires create a lot or particulate emissions from road travel.