power cord directionality

Are you joking!!

IE:  ALTERNATING CURRENTThat is the key word!  Current alternates direction.  Yes, DC power does exist, and transformers are DC to keep from blasting everything with a 60 cps hum, but interconnects and speaker wire?   NO!   Think about it.  Current for a 400 cps signal, for example, goes back and forth 400 times per second.  It does not flow like water.  The current driven magnetic force pushs the speaker out 400 times a second and pulls it in 400 times per second.  It does not push and rest.  Directional wiring for alternating currents, such as for fuses, speaker, and interconnect wires, is pure witchcraft, i.e. fantasy.   If you do not grasp this, I have some magical, one direction, magiquark driven fuses for sale.  Call 1-800 One Muon.

Magiquark fuses??!
How much?
Are they marked for directionality?

When we talk about A.C. power or POWER Cords, there is no Physical science that specifies "polarity"

Polarity on A.C. power is mainly for safety. In the off position the device can be safely serviced because there is zero power after the power switch. This is why the HOT side of the cord is directly connected to the power switch. 
As for a device not equip with a power switch be careful.

U.L (underwriter labratories) is the largest testing facility in the U.S. tasked with safety testing things like power cords. I would venture to say that in this era, inorder to get the U.L. listing a device not equip with a power switch would require a polarizes power cord.

A picture is worth a thousand words. The signal travels in two directions 🔛 as it alternates at whatever frequency applies, as someone said. But you only care about the signal when it travels in the direction of the speakers. You can forget about the signal whenever it’s traveling in the opposite direction 🔙 because it doesn’t affect sound quality. The only signal that affects SQ is the one that is traveling toward the speakers. 🔜