I'm a lot more worried about the US overreacting to a cyber attack, or reacting to a forged country of origin. That seems much more likely than overthrow of the government. The day the US government said that cyberattacks could be considered an act of war, I'm sure there were numerous smaller countries and non-state actors scheming ways to make it look like Russia and/or China wiped out the US financial, government, military, and SCADA computer systems, triggering a physical war. It's kind of like the supposed automated USSR doomsday retaliation scenario, except anyone can pull the trigger.