Internet2 is awesome.... Canadians rock for coming up with that stuff.
Anyway, in theory, the internet can't be taken out with a single attack, or even multiple... it would take some pretty precise and knowledgable work to take it down entirely.
That being said... who here hasn't experienced major lags, websites that won't connect and very slow speeds anytime a major backbone has a router go down?
Take down a few of these:
http://www.internetpulse.com and it might not be destroyed, but it would be practically unuseable.