And if my grandmother had wheels, she'd be a bicycle. The odds of the US or Britain improving their rail systems in order for them to be more efficient/usable are vanishingly slim, to the point that we should likely bake their crappy nature into our assumptions of requirements.
We can't even figure out how (here in the US) to build subway tunnels as cheaply as ones in Europe, if I recall right. I am very skeptical that we will ever manage to approach the ideal here, for a variety of reasons (suburban / car-centric lifecycle being so deeply embedded here, etc) which I don't think can be addressed by science. It seems like an economic problem, where paying to rebuild everything is so expensive that no one will do it in the short term, even if the long term gains could be great.