One of the things that is different about power cords vs ICs and speaker cables is there is always voltage present as long as power is supplied whether or not the device is turned on. If the dielectric is the primary thing that burns in, it seems to me it is the capacitive property of the cable that is affected and current shouldn't matter. What say ye?
I say ye R OTL. A medieval term invented by the Duke of Sandwich meaning "out to lunch": not all there.
Voltage is a differential. It is in other words measured between two things. Across a circuit. Without which (a complete circuit) there is no voltage, no amperage, no capacitance, no nothing. (Try buying a meter that can read voltage, resistance, capacitance, inductance- you name it - without being connected to anything.)
Yet another way to think of it, your imaginary voltage, which of the conductors is it "on"? A 120V circuit (there's that word again!) consists of one black "hot" wire and one white neutral wire. Normally voltage is measured across the black and white. But there is in principle no reason it cannot be measured across black and ground. Same 120V either way. But what about white/neutral to ground? Where is your 120V? Not there! So where is the voltage? Not there.