Actually, the new US diesel specs are even more stringent than Europe's at this point...especially with particulate control and I believe sulfur content of the fuel too (ULSD=15ppm S or less). The particulate traps and exhaust recirculation here (US) further chokes the diesel engines but makes our regulators happy. In '07 & again in '09 the rules became so strict that you should look at the drop in diesel offering for the US in the '09-'10 model years (BMW, Jeep, Audi, many of them disappeared). Mahindra was to bring a truck here but it never happened...

...they are just now coming back.

Our rules are different enough that it directly affects what is available on both sides of the pond.