Rail mounted seems to be outdated. they need tracks, and tracks are easy to trace or destroy. I'm betting the US already have a complete map of all train rails in Russia. There's a reason we put nuclear missiles in underground silo's......so they can't be destroyed so easily.    The problem with Russia is they do all this posturing, knowing damn well that the US is never going to nuke them unless nuked first. Although I'm sure it'll come in handy if China becomes a problem in the future.    The only way Russia could get away with a rail system is if they destroyed all satellites in orbit....but I don't think they could get them all. I'm sure the US has a few outside of the Keppler zone.