It may be something as simple as a short in the wiring, or a bulb that's of an incorrect wattage and is drawing too much current. I'm guessing that it shouldn't be anymore than 50-60 watts, but I'm not entirely sure as the Australian model doesn't come with a rear fog light.
One very quick and simple test you might like to try - if you have access to a multimeter - is to take the bulb out, set a multimeter to measure resistance (ohms), and then touch a probe each to the two contacts for the bulb. If you get a reading of 0, then you probably have a short somewhere in the wiring.
Requested wiring diagram is attached.
Ben