I don't think it's the oil lobby that keeps diesels out of the U.S.
I think it's a factor of a few things:
1. Americans have awful memories of those loud, stinking, smoke belching diesels of the early '80s and can't get past that. My friend's parents had 2 Oldsmobile diesels in the early 80s...and I remember how dreadful those things were...not to mention having to go out early in the morning on a freezing morning to warm up the glow plugs just so you could start the thing up. Not very practical.
2. Environmental restrictions. Only more recent diesels are clean enough.
3. Availability of diesel at the pump. I could be wrong, but I don't think every corner gas station has diesel...but yeah, that is changing.
4. Marketing. The need to get folks beyond 1-3.
But, jeez....you'd think that with the junk-food scarfing American public...tell them that the exhaust of bio-diesel smells like french fries vs. well..diesel...you'd think they'd be breaking down the doors to get one.
I had a 1990 Civic, and that thing got 40 mpg on the highway. The 5-speed helps, of course, but yeah...how come we can't do better nearly 20 years later??