Maybe American culture is a bit different than everywhere else. If so, enabling this different to continue might be a good idea. Diversity and all that.

Or maybe American laws make it essentially illegal to use newly-developed or redeveloped land in a way compatible with high-quality transit service.

It seems to work in New York, Boston, San Francisco, and Seattle. Of course it could be better in some of those places, but those cities could not exist in their current form without mass transit.

Or maybe not, obesity, environment costs, and all that...

Besides, is Manhattan not American? The seem to do well (though, of course, they could spend more and improve their neglected since the 70s or so subway).

Still the only city to have many lines open 24/7 and besides a few other American cities, I don't think any other city has a 24 hour line.