Oh, I found an old post of mine with Radio Service Mode instructions... I will try this when I see the car later today and report back.

OEM instructions to enter Radio Service Mode to change region:
http://www.bigpatsfans.com/radio_service_mode.pdf

BM53 withWidescreenMonitor AFTER 9/01

1. Turn the radio on.

2. Immediately press and hold the 'Select' button for at least 8 seconds. The screen will switch to Service Mode.

3. The screen will now show the serial number of the radio.

4. Use the "< >" buttons to select the desired service function.

5. Selections for the desired service function can be made by using the radio station preset buttons #1-6.

6. Turn the radio off to leave the service mode.

NOTE:
When selecting the country AREA, push the station preset #1 repeatedly until AREA USA is shown on the screen.

When selecting the GAL level, use station presets #1-6 to select level.
To turn off/on the RDS function on this radio, push the 'INFO' button and select RDS off/on