I think it's not feasible in America because of the culture. If you have a good chunk of people that are hell-bent against sharing space with others for one reason or another (some are legitimate reasons!), you're already discarding a significant chunk of passengers.
Another hot take is... if you want any of the infrastructure to be mass-used, you have to make it better than the alternatives, so people with the means would use it as well. Like your subway should be faster than the cars, so even affluent people would take it. Your trains should be faster than door-to-door flight time, so people would take that as well. Unfortunately that makes a lot of things more complicated in communities with high income disparity.
Another hot take is... if you want any of the infrastructure to be mass-used, you have to make it better than the alternatives, so people with the means would use it as well. Like your subway should be faster than the cars, so even affluent people would take it. Your trains should be faster than door-to-door flight time, so people would take that as well. Unfortunately that makes a lot of things more complicated in communities with high income disparity.