North America and Japan: Subways

A cute comic by XKCD published the other day shows all the subway networks in North America falsely connected:

It was interesting to me how few there are on the whole continent; that map even includes Mexico and Canada!

For comparison, here is a subway map of just Tokyo:

And on top of that sits this network of JR trains (plus a whole bunch of private lines mostly not listed on either of these maps):

Makes the North American map look rather pitiful by comparison.