As others have pointed out, the lack of MY2007 diesel VW passenger cars in the US market is because of the 2006-2007 nation-wide switch over from LSD (low sulfur diesel) to ULSD (ultra-low sulfur diesel) fuel. Apparently, not all refiners could guarantee the nation's fuel supply would be completely switched over to ULSD prior to the introduction of the MY2007 cars, in late 2006. The concern is that the higher levels of sulfur in the older type of fuel would wreck havoc with the new car's emissions control system.
VW increased production of the MY2006 TDI's, overstocking them at the end of 2006 in order to have an additional supply of the LSD-compatible cars to sell in early 2007, but these are long gone by now.
As regarding the issue of "pollution", there's EU standards, there's US EPA standards, and then there's the "ooh, that truck stinks, while sitting in traffic behind a semi" standard. None of these standards are, er, standard! Meaning that the US EPA is focussing on the control of nitrous oxides, while the EU is more focussed on global-warming gasses like CO2; therefore the two regions have different pollution standards that mandate differences in, not only hardware design and implementation in passenger diesel cars, but also mineral and bio-based diesel fuels. Whereas the average person with a sensitive nose is really reacting to particulates.
Personally, I like the smell of my 1998 Jetta TDI's exhaust, especially right after a synthetic oil change. Kinda smells sweet. Certainly more appealing than the rotten-egg, hydrogen sulfide smell from the tailpipes of gasoline cars with catalytic converters.
Of course, I won't mention acid rain....