Trains DO work as the primary mode of transportation in NYC... But aside from that, you're right that electrification won't work everywhere for passenger rail in the U.S.A. However, there are several routes (Dc-Boston, which is actually electrified otl), NYC-Chicago, San Francisco-San Diego, and possibly Seattle-Portland that have a dense enough population and short enough distances that electrification/high speed would certainly be profitable if more people actually rode them, which is pretty easy to do if you get more people living within a mile of commuter rail stations so that they can use trains to get to and from work, and visit other cities with them. Additionally, with subsidies, a double-track electrified line from Chicago to San Francisco is doable. It will need heavy subsidies, but considering the fact that THE ENTIRE TRANS-SIBERIAN RAILWAY LINE IS FULLY ELECTRIFIED IN OTL it is certainly doable (Chicago-san fran is only half as long as the Siberian/low-density portion of the route of the TSR and has bigger cities along the route like Denver, salt lake city, and Reno, so while it wouldn't be profitable it wouldn't make too big of a loss for the more profitable routes to handle). So while trains won't be able to cover everywhere like they used to, a Chicago-LA overnight service is quite possible ittl. Don't forget that cities like Minneapolis, Columbus, Indianapolis, Pittsburgh, and more can be serviced by spur lines.