The (British) Union Flag was still regarded as the National flag by many Australians well into the 1970s, which inspired Arthur Smout's campaign from 1968 to 1982 to encourage Australians to give the Australian flag precedence. Australia continues to take a lot of cues from the mother country even today - something you'll notice if you've been to both the UK and Australia.
That's because they're part of the British Commonwealth. But I find is a bit odd that government forms didn't change in the 55 years between Australian independence and Obama's birth.