Don't be silly op, we do have those in the US except their buried below ground and the system in place is not for the every day common Man. There is not one "National Park" that doesn't have access to the system, but if you go wandering about on a hunch to find the secrets then you will become a statistic and your miserable death will only be known to you and the small group of death dealers that thrive on being exclusive evil clowns.

There's a map floating around on the interwebs that shows a layout of all known underground tunnels and caves, then superimposed right over that map is a map of "missing persons" and their last known whereabouts. But alas, buried in the pile of other "conspiracy theories" it becomes less known about by design, but do research if your brave enough and you will see something intriguing.

It is said that one can easily and hastily travel from one coast to another underground by only changing trains 3 times. While the body doubles distract the peasants the real snakes travel on rails below.

On the other hand, why would they indeed bring such expeditious travel options to a populace their trying to herd into 15 minute prison cities?

Carry On!!!