I don't think there's much point in thinking about that change, because in the US there isn't the political will to operate and maintain such systems on an ongo

I don't think there's much point in thinking about that change, because in the US there isn't the political will to operate and maintain such systems on an ongoing basis. The NYC subway + DC metro, while far from perfect systems, are basically built on the desirable "traditional city" model. In both cases, actually maintaining and funding the system to operate to a reliable and acceptable standard, instead of running it into the ground, is a controversial idea with limited political support. Unless and until such things can be operated as a going concern on an ongoing basis, there is no point building any more.