[dheera]

Most passenger US rail systems have APIs with realtime positions but I don't know of a single map that includes all of them in the whole country.

Here's a live one for Boston: https://tmap.live/

Here's a live one for NYC: https://aptransit.co/

Here's one for Amtrak: https://amtraker.com/map

For your son though just get the "Transit" app by CityMapper