I'm not too sure Australia would be unaffected, there are quite a few US bases / radar stations etc on Aussie soil...the Chinese/Russians may not like it if it came to a head..Antarctica and Greenland maybe?
Well you have to consider the size of that continent. I am not saying it would be 100% unaffected but remote locations like North-West Australia has literary nothing there to attack. Some small towns and that is it.