There is a reason why AMTRAK exists, because there's no way to make money off a national rail passenger system. The only route that I believe generates any decent amount of money is the Acela/North East Corridor.
Also, AMTRAK trains operate with the lowest priority when traversing UP/BNSF/N&S/CSX rails. They're frequently delayed up to several hours sometimes as higher priority freight goes by. Even if you could cruise at 79MPH or faster due to better quality gauge rails, whats the point if you're going to be waiting at signals or being stuck in a siding waiting for freight to pass at 30-40MPH.
There are certain corridors where high speed rail makes sense, but is Chicago - St. Louis really one of them? Besides, how about focus some of that money back into putting metropolitan rail/commuter stuff into being a priority. Traffic still sucks in many US cities.