Looks like only Australia and New Zealand require a lower sulfur content than the US: http://en.wikipedia.org/wiki/Ultra-low-sulfur_diesel.

"The transition to ULSD is not without substantial costs. The US Government has estimated that pump prices for diesel fuel will increase between $.05 and $.25 per gallon as a result of the transition. And, according to the American Petroleum Institute, the domestic refining industry has invested over $8 Billion to comply with the new regulations."

In Europe, they also subsidizes diesel prices. In the US, we subsidize corn-based ethanol. Go figure...