Overfilling the tank can force fuel into the vapor canister–the device intended to store gasoline vapor until the car can purge those vapors and burn them rather than vent them into the atmoshere. Liquid fuel can deteriorate the charcoal in the canister, turning it into small granules that can in turn travel through the rest of the system and stick in valves and solenoids.
The fuel system may also use a fuel tank pressure sensor, which operates just like the MAP sensor on the engine does. This sensor my be damaged by repeated immersion in fuel.
Some cars use a “leak detection pump” which draws a slight vacuum on the fuel system and watches for a leak. This can also be damaged by liquid fuel.
I’m sure there are other things I’m not remembering right now.