My thoughts are that, with three very active fronts (Europe, Korea, Iran), the U.S. wouldn't be in a position to send much of anything to Australia, other than what happens to be there at the time (probably a few ships/aircraft/troops in transit to other theatres, and that only on a very temporary basis.
There's just nothing left to send, by '98, and that's straight from the canon.
I think your "thoughts and prayers" comment is right on the money. To put it in T2K terms, though, it'd be "Good luck. You're on your own."
One thought that just occurred to me is that a few hundred/couple thousand U.S. military personnel could be in Australia on leave (common enough during the Vietnam War) when the Indonesians attack. With no safe way to return to their posts (likely in Korea), they're stuck there and formed into an Ad Hoc "American Legion" under Aussie command. This could be a fun way to incorporate American PCs from any of the U.S. Army, USMC, USN, USAF or even USCG units in the Korean canon (which the KPSB follows closely) into an Australia-based campaign.
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