This is incorrect. The vehicles listed here mostly use a Urea spray mechanism that needs to constantly be refilled in order to comply with US diesel contaminant laws.
You are correct that gas is subsidiesed to a much higher degree in Europe then here.
It's just
taxed less. No fuel for private vehicles in either jurisdiction is subsidized.
The urea spray solution isn't for US
regulations (there is a difference, remember, the EPA deems the American people irrational, and by extension, stupid:
link), it's to comply with the more stringent EU regulations. But because those regulations were not invented here, all new models of light duty vehicles must be tested, in each configuration sold, to be admitted to the US market. So that TDI Golf in Europe's engine was tested in one configuration, and the emissions extrapolated from there. Here they add a sunroof, and you pretty much need a new test (which comes with a few thousand dollars' worth of filings and a few hundred thousand dollars' worth of legal fees of course).
Why urea injection? Because Peugeot came out with their catalytic converter diesel engine in 2003. It didn't smell like a diesel, and with the backpressure controls it didn't sound more like one than the dual VVT-i our 4Runners come with. It was awesome, and they dropped into their "best" car, the 307 hatchback, a direct competitor to the Golf. I still remember that commercial, it was pretty funny, with a German businessman renting a car in France and having specified a diesel engine, and bringing it back because it did not stink.
The Germans literally poo-pooed it in the European automotive press. And that year they could not give their diesel cars away. Much crow was eaten in the following years. Sometime around that EU5 was published. And management still can't admit they're wrong, so they made their engineers come up with something other than the catalytic system Peugeot used.
VW ended up paying up to Peugeot and licensed their catalytic converters, as did BMW. Or holes were found in the patents. Only Daimler steadfastly refuses. Which is why Mercedes light duty and passenger vehicles need urea.