This is the same reason the Navy has for building ships in the US even though they can be done other places cheaper.
Maybe in 1942. Modern tanks cannot be built on highly specialized production lines that build road vehicles without years-long re-tooling. M1 Abrams tanks don't even use piston engines, they have turbines.
A older, but well documented example how specialized modern automotive production has become is the Mercedes Benz 500e. In the 90s Mercedes wanted to build a more powerful, wider version of the E class. They added 56 mm to the front fenders and discovered it wouldn't fit through the production line properly. MB contracted for Porsche to handle the low-volume 500e on a different production line.
You'd think the biggest war machine on the planet would benefit from economies of scale by now. If they want to stay sharp they could build commercial ships between the ocassional war ship.
If you do believe in it, then it's simply irrelevant. Given the other reasons that the US military is spent with profligacy on US manufactured goods, maintaining 'truck know-how' does not register. If the know how consideration did not exist the money would still be spent in exactly the same way.
Even if you repealed CAFE today, the automakers have all built their entire business strategy around selling enormous expensive vehicles and generally despise producing lower cost options.
We are starting to see what appears to be the beginnings of a small pickup renaissance due to electrification but none have actually hit the market yet and trump has further stalled that progress by messing with EV subsidies and environmental standards.
I am sure they could consolidate the models to work in both the US and abroad, but my guess is they do enough US volume that it is not yet advantageous to do so. There's already a number of major parts that have been shared recently between the Tacoma and Hilux... e.g. the 2TR-FE engine and AC60 transmission. But usually Toyota chooses to spec the Tacoma as a more up-market vehicle, which makes sense given the US market.
If it existed they would fill every rural high school parking lot in the south. Allow them to exist and someone will build them.
I like my big truck but when it dies, if there's a small truck available that lets me plow snow and tow logs in the forest, I'll get it.
The thinking was it would make cars more efficient but instead everyone just built obscenely large vehicles that were classified as trucks instead of passenger vehicles.
The first one is a trade off against cost, but the market is already pretty good at handling that one on its own. Fuel injection and aerodynamics don't add much to the cost of a car, so pretty much everything has that now. Hybrid batteries are more expensive, but the price is coming down, and as it does the percentage of hybrid cars is going up. You don't really need a law for this; people buy it when the fuel savings exceeds the cost of the technology.
The second one is a trade off against things like cargo capacity. If you say that "cars" have to get >35 MPG at the point before hybrids are cost effective, or keep raising the number as the technology improves, it's essentially just a ban on station wagons. And then what do the people who used to buy station wagons do instead? They buy SUVs.
The entire premise is dumb. If you want more efficient vehicles then do a carbon tax which gets refunded to the population as checks, and then let people buy whatever they want, but now the break even point for hybrids and electric cars makes it worth it for more people.
Automakers simply hate making affordable cars. MBAs extol "Number must go up! BRRRRRRR!" and you cannot do that with cheap cars.
Remember the 70s? What did the big automakers do? They made bigger and bigger cars ever shittier and jacked up the prices. Sound familiar?
And then what happened? Japan showed up and cleaned their clock. And then the protectionist laws got passed, but it didn't matter because the Japanese cars were smaller and better and used less gas. Sound familiar?
History may not repeat itself, but it sure likes to rhyme.
“We have such sights to show you!”