Because it's not cost efficient for manufactures to conform to US air quality regulations. None of those diesels overseas have particulate filters. They aren't required to have the additional thousands of dollars of equipment on their vehicles to combat poor diesel emissions.
This is also America. Where we have 800 cars for every 1000 people. In Europe, the ratio is closer to 560 to every 1000. We could singlehandedly, as a nation, destroy the atmosphere in a matter of decades.
Yeah, what [MENTION=87531]FrontRange4Runner[/MENTION] said. I'm just too lazy to type it out.
EURO5 emissions for diesels are more stringent than California's diesel emissions, and all the manufacturers sell compliant engines. Even with EURO4, there are engines with 200,000 miles on them, and few issues. Diesels are still a heck of a lot simpler, and certainly not more complicated, than gasoline engines aiming at the same emissions specifications.
The problem getting diesels to the US:
1. the cost of EPA and CARB certification. Since apparently the air is different here, they won't accept the test results from the euro-spec tests, and the return just isn't there for something that'll make up 5-10% of the sales volume.
2. Europe has gone sulphur-free in their auto diesel fuels, which makes the emissions targets much, much easier to meet. The "ultra-low suplhur highway fuel" sold here has more sulphur in it than car diesel in Europe probably ever did.
Maintenance:
Becoming a master mechanic in Germany requires almost as much education as a medical doctor, and is respected to nearly the same extent. Here all one hears the girls say is "if you were a
good liar you'd be a laywer!" when you answer the question at a party of "so what do you do?" with "mechanic."
So like politicians, you either need to love it or be a crook to want to be a mechanic, or any type of tradesman for that matter, in north America.