I don't have the facts, but it seems like every time diesel starts to get popular in the US, the EPA nails diesel cars with stifling regulations.
FYI:
People have been paying up to $30,000 for these cars for several years.
see: http://www.ecoautoinc.com/
Not just the EPA killing it. The biggest problem is that the American automakers are so bad at doing diesels that consumers have soured on them.