Here's a great link referred by friend and planning compatriot Emily Picha: Simple line maps of 44 of the world's rapid transit systems, all shown at the same scale. It's interesting to see both the area covered, and the geo-spatial strategy employed. Some have hub-and-spoke arrangements (Chicago), others add circular routes (Berlin, Moscow), and yet others are veritable spaghetti bowls (London, Paris).
The scale of the Paris network looks a little off (too small), but I have no supporting evidence. Either way, one thing's for sure: North American rapid transit networks pale in comparison to many in Europe and Asia.
http://fakeisthenewreal.org/subway/