Even if we put 100% of freight on trains, and expand the existing rail network 10x, the need for trucking infrastructure would not decrease by any significant amount. Trains can’t stop at every single business that needs freight, and trucks are still needed to get that freight from the railport to its destination (this is called “last mile” freight, but it can be up to a few hundred miles depending on where the nearest logistics hub is compared to the destination).
By the way, we already use trains significantly. Look up the intermodal logistics network. The general concept is smaller trucks pick up freight from different businesses, consolidate it in a single warehouse, then the freight gets put on full size trucks to move to the nearest railport and the trailer is loaded on a train which carries it as far as possible, then the reverse happens at the other end. The vast majority of freight movement uses this method.
My point is that long haul is a very small minority of long-distance freight. Anything that can fly, does. Anything else will go on a train if a route exists (this is where rail expansion would help, but there are other problems with that we won’t address). The only freight that travels long-distance is truckloads that can’t fly (hazardous goods that are dangerous to put on a plane, or stuff like certain foods that could be damaged by the pressure changes in flight) AND doesn’t have a good train route to take. My cross-country routes were always stuff like fresh produce or other foods that would be damaged by the pressure. Everything else would travel a few states, but never from one coast to the other.
And you can’t put 3 full pallets on a bike, you’ll always need trucks to some extent.