According to post war declassified intelligence reports Japan didn't plan to invade Australia because of troops tied up in North Asia to meet the Soviet threat and occupy China.
In fact it is Soviet and China that carried the heavy weight in WW2. 80% of Nazi soldiers expensed on Russian soil and 2/3 of Japanese infantry on Chinese soil.
US did a great job in Pacific Theatre and should be commended no doubt, however by then Japan already lost the war. Soviet Union already promised Allies to attack Japan after Germany was defeated, it was just a matter of time. US lost more people to accidents than soldiers in WW2, while Soviet lost 20 million people.
