Size the issue here, not speed. The existing freight rail system is already faster than sending ships through the Panama canal. Rockets are particularly large and unwieldy to transport, and if Falcon 9 can’t be transported by rail, there’s no chance Terran R (which is wider) could be.

Building a separate transcontinental railway with a wider track gauge and larger turning radius solely for transporting rockets (and maybe wind turbine blades?) seems unlikely to be worth it.