The interstate highway system was actually for defense. Moving things from coast to coast was far to difficult.
FDR saw the German Highway system during the war and was rightfully jealous.
Roads are quite expensive, and there are many internet resources with tons of evidence and arguments about this: strong towns, not just bikes, climate town, etc.
Point to point navigation has high utility and is difficult to acheive with rail.
Minimum viable roads are actually quite inexpensive: clear large vegetation from the path and there's a usable road. You can incrementally improve with path markers, grading, gravel, pavement, etc. Minimum viable rail is a much higher standard, which needs grading, railbed preparation, laying the rail, signalling and operations.
Once upon a time we didn't have the interstate system, but FDR created the New Deal, and with that the federal government created the interstate highway system we have today. We can do the same for rail, but the automobile lobbyists won't allow it.
I'd argue that the interstate highway system is probably the USA's greatest accomplishment, and one of the greatest public works projects. FDR sold it by framing it as a national defense initiative.
Maybe we need to use some of that national defense budget for public transit? Sadly, I don't think we'll ever have a politician with the kind of gumption necessary to save ourselves from ourselves.