Congress could deregulate passenger rail and allow competition. Amtrak is a government monopoly. There's the chance that passenger rail isn't profitable and that it disappears but I've always thought that would be unlikely
Amtrak is publicly owned. I'd personally love to see it privatized, but you phrased that like you think Amtrak is a private company that receives subsidies. It isn't, it's closer to the USPS model than that.