How Egypt did (and how your government could) shut down the Internet
arstechnica.com
arstechnica.com
[1]:http://en.wikipedia.org/wiki/Titan_Rain [2]:http://en.wikipedia.org/wiki/2007_cyberattacks_on_Estonia [3]:http://en.wikipedia.org/wiki/Cyberattacks_during_the_2008_So... [4]:http://en.wikipedia.org/wiki/2010_cyberattacks_on_Myanmar
However if you really wanted to just cause some mayhem. With a good map and a chainsaw lots is possible.
California is trickier, there will be lots of links to towns in other states just because the cable run was shorter or a telco in Oregon wanted more of the market. There will also be a more complex backbone links so someone in Seattle may connect through california to Texas, so blocking out those individual routes without killing the whole network is a lot more difficult.
Perhaps a better approach is to work to decentralize as much of our existing infrastructure as possible. Eliminate DNS. Fundamentally change how routing occurs to become more organic. Etc. Non-trivial, to be sure, but possible, IMO, and I think it needs to happen.
The goal should be that any internet-enabled device can mesh with the internet from any other internet-enabled device. Example (contrived) would be my cell phone talking to your cell phone with bluetooth, your phone talking to your laptop with a wifi connection, and your laptop talking to another device via ethernet, etc... and that ultimately, packets flow and end points can find each other all without central routing tables or artificial hierarchies, etc.
I don't have any good ideas about what could possibly cause that to happen, but I'm pretty sure that if it does happen then things are sufficiently screwed up that a lack of internet access will be the least of your problems.
Distributed DNS etc doesn't really help if all the cables in and out of your country run through one building and the government owns it.
Old school HAM, AX.25 and Linux ~ http://tldp.org/HOWTO/AX25-HOWTO/