Ironically, a big part of the problem were the environmentalists. The mandatory transition to ULSD (Ultra Low Sulfur Diesel) in 2007 wreaked some havoc with existing diesel engines particularly in colder climates. The fuel had less lubricity and less resistance to water (microbe growth, etc) such that older engine designs were requiring alterations. Other designs were failing because the solvents were breaking down the oils internal to the engine too quickly.

It was simply easier for the manufacturers to stop selling diesels in the US. Diesel fuel outside the US didn’t have the ULSD change.