Bubsy, the voltages to which you refer 120 and 220 are the electrical voltages that come through the wires and into the PSX when you plug it in. Those voltages are converted by the PSX to the voltages that Bgnome mentioned to power the Dual Shock motors. If the 120 or 220 voltage went straight to the Dual Shock motors, poof!!! fried Dual Shock controller.
I have heard, also, of people buying European or Japanese controllers and plugging them right into an American PSX and vice versa. So you shouldn't have any problem w/using an American controller w/your European PSX. Hope this helps put your mind at ease.