Within a guitar the tiny loop created by running a wire from pot to pot and the copper of aluminum foil between the pots is insignificant. There is virtually nil significant current flow to cause a noticeable voltage drop within the guitar, and no way for it to get out of the guitar to the amp. Inside a guitar the biggest voltages that an amp will respond to will come from the pick ups...

Ground loops between guitar amps and mixing consoles and guitar pedals pose the more serious/annoying problem... These days near everything has an Earth pin on the power plug so for the most part everything has a similar voltage on their exposed metal parts. The earth loop problem rears its ugly head when two connected devices obtain their power from different outlets, and one of those outlets also has a high power consumption load (such as an air conditioner or very high powered amplifier) on its circuit.The voltage drop caused by the high current load (the air conditioner or whatever) is often "seen" by the guitar amp or mixer and presents as 50Hz or 60Hz buzz in those devices. Simplest remedy is place all your music gear on one circuit and series of outlets, and place the high power consumption load (the air conditioner) on its own separate power circuit and outlet. It is the minuscule voltage difference between various audio devices that manifests itself as mains power frequency Earth loop buzz.

In most home studio situations the use of power distribution boards connected star fashion for the entire audio system helps greatly reduce the chance of earth loops ever appearing... In big PA systems and large Pro studios special precautions and techniques are employed to minimize Earth loops.

There are guitar amps that also have a built in anti Earth loop feature. Separating all the amplifier internals from the chassis ground with a 5W 10 ohm resistor will often relegate Earth loops into non-existence. Early VOX amps were all fitted with said 10 ohm resistor. Many modern amps don't, and are engineered and built in a way that the resistor is (hopefully) not required.