Well i have read more on the respective nations of Australia and America

According to Ellis

1, Australia had a population of 6,900,000
Total service personel during WWII 1,350,000
which in total comes to 19.56% of total population serving
leaving 5,550,000 to sevice the ecconomy and keep the nation running.
remove 50% pertaining to children and aged that leaves an available
workforce of 2,775,000

2, America had a population of 129,000,000
Total service personel during WWII 16,500,000
which in total comes to 12.79% of the total population served
leaving 112,500,000 to serve the ecconomy and keep the nation running.
remove 50% pertaining to children and aged that leaves an available
workforce of 56,250,000

Overall the the US had available 20.27 time the workforce than Australia.

America could not have done all the things it did with a workforce of 2,775,000.