The US interstate system is incredible extensive, uniform, and well-maintained (relatively speaking). States love federal dollars, and if there were federal dollars for train lines, they'd fall over themselves to get them. That doesn't seem to happen for a lot of reasons. It seems like there are a lot of corruption problems that seem to eat up train projects, but for some reason the interstate system, though replete with plenty of boondoggles, is an unstoppable road-spreading machine.
The interstate system only succeeded because the federal government took the very rare step of steamrolling all the states and individual landowners. It was done in service of putting people to work and stimulating the economy. But it was not a well-liked project.
Today, it is well-regarded, but when it was being done? No way.