It's not so much that American companies do pickups and SUVs best, it's that the Asians don't do much of it. The only reason Americans don't want compact cars and sedans from GM, Ford and Chrysler is because those cars mostly suck compared to the competition.
Americans are still buying compacts and sedans, but we're mostly buying them from the Asian manufacturers:
https://www.statista.com/statistics/276419/best-selling-cars-in-the-united-states/
Everyone here is familiar with the durability and customer satisfaction consumers have with the Tacoma, Tundra and 4Runner. Imagine instead of just Toyota and Nissan in the truck and truck-based SUV market, you also had Honda, Subaru, Mazda, Mitsubishi, and Hyundai. That would make life very difficult for GM, Ford and FCA.