@clearthinker +100 to:"the wire gauge needs ONLY to be thick enough to carry the current being drawn by the component to which it is connected"
end load in the AC power line typically is a power transformer, which has primary and secondary winding (primary gauge is up 100m long with high gauge), anf total effective resistance limits max current of power delivery network for that particular load. amp/pre/etc have primary winding resistance in the range of 0.2..50Ohms, which is significantly higher than ANY power cabe’ discussed. power transformer's resistance sums with protection fuse and internal wiring, which adds resistance to the AC power line as well.