And the wire gauge from the IEC inlet to the power supply is at most 14ga and is usually 16 or 18ga. Not to mention the fuse element is equivalent to a 20ga solid conductor.
I use 10/3 Romex for one reason only: the conductors are pre-twisted in the sheathing and that goes a long way into reducing common mode noise. I steer away from 2-wire Romex because the conductors are parallel and flat, making them a very efficient RFI antenna.