Earlier quoted context omitted.
Which makes me wonder, is there a way to make an ad-hoc, decentralized internet that a government could not shut down?
It's arguable, but I'd say that the real Internet is like that, at least in well-connected places like the US. I cannot imagine the act of God necessary to stop Americans from accessing Google.
All it takes for the vast majority of the internet to become unusable for the larger fraction of the population is to take the .com, .net and .org TLDs down. Your packets will still route but where do you want them to go? It would take long enough for people to regroup and find work-arounds that more permanent ways of blocking access could be rolled out.