I hope we never find out what happens if the US internet goes down. But with 2020's track record and what 2021 is starting to look like, we might find out!
Outside of a rogue president that convinces the military to act in illegal activity or a true government overthrow it won't happen.
No running or existing government in the USA will pull the plug because they know that would end their career. All their fundraising gone. Wall Street RIP. Riots all over the place.