The Internet Storm Center has a somewhat more even-handed breakdown of the proposed legislation: http://isc.sans.org/diary.html?storyid=6124 The “shut down the Internet” part can be found in S.773 §18 (2): ( http://www.opencongress.org/bill/111-s773/text?version=is... ) > [The President] may declare a cybersecurity emergency and order the limitation or shutdown of Internet traffic to and from any compromised Feder…
The President might define "critical infrastructure" as being the entire Internet- and many other countries route a large portion of their Internet traffic through the US- so a shutdown in the US would certainly slow down, if not shutdown, much of the rest of the world.