>Imagine everyone had their routers disabled simultaneously. I don't know if the cell networks could function with the surge in standard traffic that would happen, and then you've effectively plunged all or part of the country into a communication blackout.

IME cell networks definitely can't cope with a loss of all routers in an area, given how mobile data becomes basically unusable when there's a power outage. That said, "everyone had their routers disabled" is probably not realistic, given that there are plenty of non-chinese router vendors.