What if US had a train run parallel to every highway?

We kind of do. It's just that the tracks are owned by freight companies BNSF, Union Pacific, CSX, or Norfolk Southern. Take a look at their system maps.

BNSF: https://en.wikipedia.org/wiki/BNSF_Railway#/media/File:BNSF_...

UP: https://www.up.com/aboutup/reference/maps/system_map/index.h...

CSX: https://en.wikipedia.org/wiki/CSX_Transportation#/media/File...

NS: https://en.wikipedia.org/wiki/Norfolk_Southern_Railway#/medi...

Canadian National Railway and Canadian Pacific Kansas City fill in a few gaps in the US and extend the system to Canada and Mexico. Throw in Ferromex and that covers most of North America.

We have the trackage, we need to find a way to put passenger rail on a better footing against freight carriers. See https://www.youtube.com/watch?v=qQTjLWIHN74