OK, sorry for the delay guys. I finally got time to go get some images.
Below is the JDM A/C condenser with its single-wire connector and to the right right of it, the USDM WRX three-wire harness connector.
A close-up of the JDM A/C condenser connecter:
And the USDM WRX connector with each lead labeled 1, 2, and 3 respectively for ease of identification.
Last but not least, here are the matching connectors off of the JDM wiring harness and the USDM A/C compressor that I salvaged. The leads on the USDM WRX connector off the A/C condenser itself are labeled a, b, and c. When the USDM WRX A/C compressor is connected to the matching wiring harness, the connection is as follows:
1 - a
2 - b
3 - c
Now, all three leads off the USDM wiring harness do not show a change in voltage when checked against a ground before and after the A/C button in the center console is pressed. Hence, I believe it is an issue with the different pin designation/wiring of the JDM STI and USDM WRX ECU. Unless, as Chad mentioned, connecting/looping wires on the harness(es) will make a difference.