I think there are a couple factors. The first is the fear of the unknown, which is a little strange because 99% of the people driving cars know nothing about the mechanics of a car, so it really should be irrelavant whether they drive a gas or diesel powered car. Additionally, there is the stigma, as already mentioned, that diesels are garbage because GM produced some really awful cars back in the '80s.

Then there is the ego factor. Many, many Americans make a car an extention of their ego, which means they don't feel "man enough" or "cool enough" unless they can spin the tires in their car, or drive something bigger than the guy driving next to them. Just think about the cubic inch wars back in the '60s and '70s, or the fact that every soccer mom in the country now has to drive a huge SUV with a gas-sucking v8 in it. Its all ego. And since a diesel powered car or truck is slower, it just isn't acceptable to Americans - who, buy the way, can buy their gas far cheaper than people in just about any other developed country in the world, so why would they bother with diesel?

GregS
'84 300D, 173k
'90300CE (but I wish it were a 300CD!)