Word I got was that Egypt was able to cut off the internet because the state runs the main connections to the www and landlines.

Twitter, using wireless connections, some of which cross international borders, was far less successful. The leadership was not up to date on their plans for dealing with an uprising. This was made clear when the government sent troops to surround the TV and radio stations. This would have been fairly effective in controlling the media in the 80s but now it just highlights how out of touch the ruler was.

Political observers also noted that turning off access to the internet seems to have backfired. When the internet was available many people would spend their time raging and letting off steam on the internet. When the connection was lost people lost the last outlet for their frustrations and ... wait for it ... went out on the streets to protest.

The US telecommunication system, highly integrated across media and platforms, with many redundant paths to get virtually anywhere, would be much harder to control. It wouldn't be impossible, just much more complicated and difficult.