That's a bit of a fallacy. They compare the US to single European countries. I'm guessing it would be as easy to turn off the internet in California as it would be to turn it off in Greece.
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.