"As far as Oz goes the sheer distances involved from north to...

"As far as Oz goes the sheer distances involved from north to south would have played a major role in the eventual outcome- I wouldn’t be surprised if it would have ended in some kind of agreement between our two governments.
( we did have a plan to retreat and concentrate on the southern states )."

The Japanese were already bombing Darwin and some towns further south. They would have been able to occupy the northern part of Australia and gradually advancing south. Australia lacked the numerical strength to fight a sustained war against them, even with the advantages offered by the vast spaces and the desert.

The people who are criticising the Americans for going against the Japanese want the Japanese to own Australia.