The US already has one of the largest freight rail networks in the world (at the expense of having a totally shitty passenger rail network; although that's starting to change with Florida and California's efforts).
I wish more effort would be put into expanding freight even more so you could get the same speed and efficiency for shorter hauls, mail and package delivery. It seems like that would be way more worthwhile than automated trucks. It's substantially more trivial to automate freight trains as well. Passenger trains in Singapore, Malaysia and parts of London are already fully autonomous with no driver at all.
The U.S. used to have extensive short-haul rail, even inside cities. That's how cargo moved around back in the era before inexpensive motorized trucks.
I suspect the reason it disappeared is that rail sidings are large and expensive compared to truck loading docks. You're not going to have ten sidings on a property as easily as you stick ten bays in a loading dock.
I wish more effort would be put into expanding freight even more so you could get the same speed and efficiency for shorter hauls, mail and package delivery. It seems like that would be way more worthwhile than automated trucks. It's substantially more trivial to automate freight trains as well. Passenger trains in Singapore, Malaysia and parts of London are already fully autonomous with no driver at all.