Ok, that’s a good question to raise, but maybe you should move beyond asking the question and try answering it. You could learn about how different shipping methods are used, how they interact, and just how extensive a rail network a country as massive as the US would require to replace roads. You could also consider that withnthe death of those roads, you’d be utterly snuffing out smaller rural communities, which would be too small or too distant from major population centers to justify a massive rail project.

All in all, if you have such a strong proposition about not paying for roads, it seems like you should already know these things. Now, could roads be replaced? Probably, at enormous cost both financial and environmental. Building massive rail networks is not quick or cheap, you’re talking about megatons or steel and iron being welded after all.