This is called the AI Stop Button Problem. Computerphile has a great video on this (featuring Robert Miles) which explains why this is not a reliable solution to AI getting out of control. When the AI is smarter than all of humanity combined, the only real solution is for the AI to not get out of control in the first place.
If people are going to produce unrealistic sci-fi videos they should at least try to make them entertaining and not just lame.
The AI would have redundancy, both in terms of its power source and also because it can literally replicate itself and have multiple instances running all over the world.
Also, an army of drones that you'd have to dodge just to go anywhere near any critical infrastructure.
It's hilarious that your think you know what "AI" would have when it doesn't even exist
It's only a little bit comforting that computers still live in meatspace when you consider something like an AI-controlled Metal Gear roaming around though.
2001 Space Odyssey presents a different scenario
It does exactly present that scenario, as Dave Bowman gains access to the circuit breaker (well, to the memory banks).