making a functioning train network for the US would be something that would have to overhaul the entire logistical network

We have a massive network of legacy rail to exploit. What has been talked about largely involves upgrading and retrofitting existing lines, building out new terminals and expanding old small ones. In particular, just increasing the frequency of service on neglected lines - the San Antonio to Austin route is notoriously neglected, despite being a prime candidate for cheap and easy improvement that would save millions of road hours for intercity transit and exurban commuters.

It’s one we should do, but it’s still Herculean in scope

On a national scale, it is Herculean. But at a thousand individual points, it is a very straightforward and doable job.