Its a 3-pin plug.
Outside of the price difference, there would be no issue using a console bought in AUS in the US. Its all region free and you get to pick your language and region during setup once you log into your XBL account. In regions where the X1 is not yet out, a person would have to use a credit card from AUS or prepaid cards in AUS currency in order to access XBL, but since the US is already supported, that doesn't apply.
Of course the power plug might be different, which would mean you would have to buy an adapter. What's the power plug standard in AUS?
I've noticed that most new consumer electronics items are coming with adapters for separate regions in the box (Like a clip-on plug for the power suply) here in Aus, so you might not even need to purchase a separate adapter; its probably in the box already.
It's important to note that to use an AUS device in US you are not only needing a plug adapter from Type I to Type A, but also need a step-up voltage transformer
. Don't forget that AUS and most other parts of the world use 220-240V at 50Hz, but North and Central Americas, Saudi Arabia and Western Japan use 100-127V on 60Hz.
And not to mention these important touches:
Take note on both the input and output voltage and frequency used on the Xbox One PSU, because of this.
Frequency is most likely to affect clocks and devices with motors. They may run faster or slower than they should, and may be damaged in the long run as a result. Again, though, some motorised devices may function correctly on either 50 or 60 Hz—especially if they also operate on batteries. Just look on the label or plug.
However, you still may need to be careful if you have a sensitive or expensive device that converts AC (power from the wall) into DC (battery-like current) – especially if you also need to convert the voltage. A device will convert AC to DC either to save battery power by allowing you to plug into the power mains or charge a battery in the device. The design of power supplies where AC is converted into DC does take frequency into account.
Even though 60 Hz converts a little more easily to DC than 50 Hz does, there's enough tolerance in most small appliances and electronic gadgets that you can ignore frequency. However, if you also need to change the voltage (because the voltage of your device is different from the power mains voltage), you cannot use a switching-type converter. You must use the heavier iron-core transformer. If in doubt, consult a reputable electrical goods dealer.
If your device won't operate with a different frequency (powerful motors and non-quartz clocks), there is very little you can do to change it. Unlike voltage, frequency cannot easily be converted, as this is set at the power plant. Foreign embassies may have to use huge generators to provide current compatible with equipment from home.
Take into account that if a device can go to low-power modes and control power schemes then the PSU is definitely outputting VDC to the device itself.