BBC News - 'Metal moles' begin work below London
100 m = 328 feet, 5,280 feet per mile, 3K miles across the US.
One mile every 16 days. 16x3000 = 48K days / 365 = 131.5 years ... so get 131 of the things and do it in a year -- I'd think the economy of scale on this would be pretty darned good.
At $16 million each, 100 of them would only be $1.6 B, so basically chump-change the way the US or even some of our businesses spend money. Apple has $100B in cash for instance.
Put MagLev trains in, take out the air so you can go fast, superconducting power lines for power transport (both for the trains, and for general distribution) and maybe coast to coast non-stop in less than an hour. For a little more detail http://en.wikipedia.org/wiki/Transatlantic_Tunnel
Certainly a project like this would get into the 100s of Billions, but if we could start thinking in terms of building "things" rather than just throwing it all down the entitlement hole, one could imagine rather different life potentials with the nation crisscrossed by a REAL "set of tubes" that moved physical movement speeds into some of the same spheres as internet time. Perhaps such a project could ignite more actual productivity and growth than even going to the moon?
Will there be a time when Americans start thinking like Americans rather than European Pensioners again??