I feel this also has a lot to do with the use of diesel. The number of passenger vehicles and light duty pickups in the US that actually use diesel is a fraction of what it was in Europe.

The emission limits being for ULEV vehicles, I don't think I have seen a ULEV truck - indeed California classifies most under the LEV banner.

None of this is to change the point around nitrous oxide emissions - the environment doesn't care whether it came from a VW TDI or a F350, just the amount.

But it is also far far easier to implement such low emission standards in the US because we just don't really use diesel like that.

And when you get to the heavy duty pickups (F250, F350, etc.), then most of that goes out of the window.