What is the point of the Clean Air Act?

In reference to the Paris Agreement story. As a retired Vet I have to add something very important.

I stand corrected if what I say is wrong. In the countries of Europe, Asia and Africa, vehicles do not have emission items. Yes they do not have a catalytic converter.

When a person purchases a BMW for example, the vehicle will not be shipped to American soil until it is properly inspected with the correct exhaust that is required. So what is the point of the Clean Air Act and such when the rest of the whole does not follow such rules? Makes no logical sense.

Lewis G Harlingen