Because the chicken tax keeps out great vehicles so the US automakers don’t have to compete. The hilux and 79 landcruiser are run of the mill workhorses in virtually every country in the world except the US and Canada. They run rings around the Tacoma and tundra. Tariffs and old world protectionism like the chicken tax are keeping the US automakers on life support, but they’re all doomed - they’re not even trying to…
The "protectionism" you cite is due to crash regulation and emissions standards.
America has 40% more traffic fatalities per km driven than the European Union and has less stringent emissions standards (especially for the Hilux's category, which is actually why giant SUVs became so popular over the years).
The US government doesn't even bother with these spurious pretexts anymore. They openly admit that they want to coddle local automakers to ensure that the government has a supply chain of transportation vehicles in wartime. It's quite literally socialism for the entire American auto sector.