Some additional thoughts:

A lot of the car-buying public (myself included) grew up in a time when diesels were pretty much universally awful.

Our gas prices are still very low compared to much of the rest of the world, lessening demand for more fuel-efficient options.

In recent decades, the EPA, as well as state and local governments, have concentrated heavily on defeating smog, rather than climate change and our reliance upon fossil fuels. This does not privilege diesel engines.

American society has enough disposable income and access to credit that the longevity advantages of diesel engines are largely moot.

Diesel engines are an "unknown quantity" to most of the car-buying public, and the few peculiarities about operating a diesel turn off a lot of buyers. Both when I worked for a VW dealership, as well as an independent that sold primarily TDis, a significant number of potential customers walked merely at the idea of having to wait for the glow plugs, in spite of the fact that TDis light their glow plugs in about half a second. That alone was too different for many car buyers.

Right now, hybrids have the eco-cache among those who can afford new cars. This has not been helped by the fact that for more than a decade, the only affordable diesel was VW, which have historically not been particularly reliable.