"...or my friend's 2009 VW?" When speaking of emissions output, I find it amusing that your anecdata involves a Volkswagen diesel.
This also then led to newer models emitting finer particulate which was more easily picked up by the wind and could travel into the lungs more easily instead of denser particulate which fell to the roadside.
Or, fortunately as it turned out. "Clean" diesel is a public health disaster in Europe. The US dodged a bullet by not jumping on that bandwagon.
The US just didn't provide the incentives to push people to buy them due to their efficiency. We pretty much said "yeah, keep driving that F-150".
It turned out that fuel economy was not the only important thing to consider. You could say we lucked into not increasing diesel adoption.
(I own a diesel vehicle with SCR, and an petrol engined vehicle, and an EV)