Is it possible to bring down the Internet for the entire U.S. like in N. Korea

With the recent news of the North Korean internet going down I have been wondering what would happen if the US were attacked in such a way. First of all is it possible (or likely) for a hacker or group of hackers to take down the Internet across the entire US? If so how? If not why not? And secondly how would a group of white hat hackers bring it back up. For instance could local groups bring up regional networks and then eventually connect them up across the country? I know this question is kind of vague but use your imagination.