“Even freight trains hauled by steam locos used to be faster than the freights running today.”
100 mph+ passenger service between major American cities was routine before WWII. Powered by steam locomotives.
But to do this requires a major roadbed investment and today no American railroad has track that can handle speeds like that.
Yes, and federal regulations induces an excessive cost burden on private companies doing that. No private railroad can just pick up a 125-mph lightweight tilting diesel-multiple-unit train from (let’s say) Siemens and run it between city pairs of its choice at the top speed of the vehicle—all because of federal regulation with respect to track classes, track signaling and even “crashworthiness” of the vehicle. Lots of mandates having to do with railroad crossings, automatic train stop systems, signals displayed in the engineer’s cab, dead man’s features, ad nauseam. Even the existence of Amtrak complicates matters.
Private railroads rebuild roadbed all the time, especially to handle increased freight business; if the feds would get out of the way, they could do it with passenger trains too.