Truth in Fiction?

Federal Response (Jericho episode) – Wikipedia, the free encyclopedia
Skylar and her friends discover that the government has also blocked all IP addresses on the internet when she tries to check her email to see whether her parents may have left her a message.
I think that this actually possible – and quite useful. If something on the scale of “Jericho” actually happened, I don’t think it would be a big deal to have the DNS changed in some way to point everyone to a specific website (or more likely a bunch of mirrored sites) that could be used to relay information.
Considering that several of the top level DNS are located in the US, it makes it more plausible that this could – and, if it hasn’t been considered, should – happen. Realistically, they could use this to redirect ALL web traffic to one place, so why not do it?