Which technologically advanced democratic countries DON'T have this capability already developed and deployed?
Do you think the 3 letter agencies in the likes of UK, Israel, Australia, Canada, Germany, Finland, Sweden, etc don't know how to turn off the internet in their countries? They'd be really incompetent if they don't.
Switzerland even had all its bridges wired with explosives from like the 19th century and all the way through the cold war to blow them up inc ase of an invasion.
Do you think the internet infra is somehow spared this kind of strategic planning?