"shut down the tubes" meaning what, exactly? a router? all routers? core or edge or both? BGP sessions? exchange points? private or public?
what I'm driving at here is that the fundamental nature of the Internet, its very definition, is a number of independent networks agreeing to exchange traffic in a decentralized manner. Even shutting down a single large provider (e.g. MCI/UUNet/Verizon/AS701) is an nonsensical statement - what specifically are you shutting down? There are thousands of routers, peering connections, internal interconnects, hand-offs to smaller providers who in turn interconnect and hand off to still smaller providers ... the architecture very much resembles a fractal for the larger providers.
Now multiply that complexity by a dozen and you've covered probably 90% of the carriers in the US ... but wait, some of these aren't US based carriers! We have quite a few carriers with circuits or presence in the US where the organization is legally located elsewhere. What do you do then?
Telling AT&T to shut down (assuming you can even define that; let's say you mean disconnect from every other provider they peer with, and shutting down their tens of thousands of client connections) would cause damage, but would do little more than isolate AT&T from the rest of the world.
This legislation is an incredibly bad idea for a number of reasons, but the risk it poses to the availability of the Internet as a whole is not one of them.