CAFE killed small trucks in part, tariffs in another part, but US manufacturers are the real reason small trucks are dead.
US manufacturers want margins, and they're not getting margins on little, efficient cars. They get enormous margins on gigantic trucks that start at $55,000. Have you noticed that all the sub $20k cars went away from all the manufacturers around COVID?
Ford makes the Maverick, which is a small truck. They were priced very reasonably at release, at $19,000 or so. However, Ford didn't make very many of them, and the ones they did make got up to $15,000 over MSRP from the dealers, who scalped them. Why would Ford want to cannibalize their pricy gigantic trucks when they know that they can get their $50k asking price because there's nowhere else for people to go?