I will disagree with you. The moment the load is removed from the circuit the generator "doesn't know" and will still be sending the same amount of energy/watts in the wires.
All I can say is, you're asking a vast number of interesting questions, but you need to focus your attention a bit. There are all sorts of different time scales on which generators and loads balance out:
- Milliseconds: Speed-of-light causality limit, which you seem to have brought up for the first time
- Short term (ms): Lights in your neighborhood burn brighter, with the vast rotational inertia of all motors and generators in the country hold frequency nearly steady
- Medium term (100ms - multiple seconds): Turbine flow control in power stations is adjusted
- Long term (integrated/infinity): Less coal burned or more water still in dam.
- Even longer term (years): Power stations getting built and decomissioned.
Now, when you're talking about instants of time so short that the speed of light does not allow a power source and load to even
communicate let alone match current, you're getting into the realm of
transmission lines. You'll note that the linked webpage there notes that the study transmission is (typically) restricted to "radio frequency, that is, currents with a frequency high enough that their wave nature must be taken into account". This wouldn't normally refer to 50 Hz power, but the huge size of transmission networks, and the newly introduced question of a device being turned off instantaneously (a hard edge with unbounded frequency content) makes transmission line theory necessary to answer your question with the sort of rigor that you seem to be demanding.
The rest of us on this thread are simply assuming that the load and generators are communicating and matching currents practically instantaneously, an assumption which a) simplifies the thought process massively and b) does not introduce any practically relevant errors when answering the question "what happens when I turn my TV off". I'd strongly encourage you to allow yourself to make this assumption, understand things within this simplified framework, and then start studying transmission lines if you're still bothered by the "spooky action at a distance" aspect. I mean, you can start developing formulae for the positions of individual electrons if you want, but none of us are going to hold your hand through that process! We're electronics people, not physicists.
Similar concept in plumbing with pipes hammering. The hammering is how the excess energy is being dissipated. What's the equivalent to pipe hammering with the generator.
That's because the water has inertia. The corresponding concept in electronics is inductance. Inductance of power lines is totally irrelevant when answering the question "what happens when I turn my TV off", except that power lines have both distributed inductance and distributed capacitance, which means they form... a transmission line. But as mentioned previously, you shouldn't think about this aspect unless you really want to. Allow yourself to assume that the load and the generator are connected by ideal, inductance-free, superconducting, short wires first.