Aren't the rails mostly owned and maintained by the freight companies?
Correct.
Amtrak operates passenger service on 21,000 miles (34,000 km) of track primarily owned by freight railroads connecting 500 destinations in 46 states and three Canadian provinces.
Amtrak only owns about 730 miles of track of its own, primarily in the NE corridor.
Is Chicago to St Louis in 4 hours really considered 'high speed?'
No it is not.
Chicago to St Louis is about 300 miles, so a 4 hour trip is only averaging 75 mph or so.
Nevertheless, this would be an improvement for Amtrak service in many areas, and represents the least expensive alternative.
The definition of "high speed" rail varies widely, depending on the specific route under discussion.
For instance, if discussing upgrades to current existing tracks, "high speed" may mean hopes of achieving 90 mph or 125 mph "some day".
Better than what we have, but still not "modern" high-speed rail by Japanese or European standards.
That technology requires all new construction of the railbed and complete separation from freight traffic. Those systems can travel upwards of 190 mph, but are much more costly than simply upgrading existing rail.
And then there is Maglev, which is state-of-the-art, travels in excess of 300 mph, and is very, very expensive.
We won’t need high speed rail. After BO is done we will need travel permits (aka carbon credits) to do any significant travel. Only approved people will be allowed to take long trips.