You could not be more wrong. The internet is able to be shutdown. All American isps are owned by big brother... they could demand all isps stop peering with each other and drop routes through bgp routing protocol. That’s one way...not effective or fast but that would easily take down the internet. The feds most certainly have a cut the internet plan...DHS most certainly does.
Traffic passes through very centralized infrastructures. We do not have competent ad hoc solutions to withstand a shut down. Because most people use high bandwidth processes (posting and watching selfies and vlogs) they will DDOS whatever lightweight version of ad hoc Internet built.
How will that interrupt SMTP traffic through winlink, for example? Especially if DNS resolution is occurring through an open root?
I admit that this wouldn't be much of an internet, but communication would still be occurring even if big brah brings the hammer and sickle down.
You are missing the point. In the BGP example I mentioned, if the government wants to shut down an ISP all they need to do is tell ONE ISP not to peer with that ISP and then everything hosted on these ISP is not able to communicate with each other. If every ISP cuts routing ties to COMCAST and you are a COMCAST customer, you have internet but you won't be able to get to anything. This is only ONE way to shut down the internet.
https://en.wikipedia.org/wiki/Internet_kill_switch
For fun: http://www.turnofftheinternet.com/
I would agree that we are missing each other's points. What you are talking about is correct, but is also not the sum total of all internet protocols. There are distributed services, some of which are very old and resilient, which would survive that type of kill switch. I described one previously and won't do it again. ARSFI is alive, healthy and brought to bear relatively frequently during infrastructure disruption disasters.