|Australia built its own destroyers and cruisers before and during WWI with the light cruiser HMAS Adelaide, commisioned in 1922, being the last Australian built warship to enter service before WWII.
Our destroyers were surplus WWI RN ships and our new Heavy Cruisers were ordered from the UK with the only new construction in Australia consiting of a seaplane carrier and a couple of sloops. Three modern light cruisers and several more WWI vintage destroyers were bought during the mid/late 30's to bolster our defences but things could have been very different.
During 1923 atoo Island quoted on the construction of a pair of 10,000 ton "treaty cruisers" based on the Effingham hull, its self evolved from the Town Class we had already built, but with three triple 8" turrets inplace of the originals single 7.2" guns. This design was knocked back on cost and the Counties were ordered from the UK instead.
I am not suggesting that the atoo Cruiser would be superior to the Counties, infact it would likely have been inferrior but that building these ships in Australia would have better prepared Austrlaias industry for what was needed in the future. Had these ships been built they likely would have taken longer to deliver than the UK built Counties which would have stretched the program enough to make ordering a second batch to begin replacing the early Town's in the early to mid 30's.
End result Australia would have entered WWII with an enhanced local production capability that would have allowed us to build the modern warships we needed when we needed them instead of having to rebuild our shipbuilding industry during a global war. We could have gone to war with six heavy cruisers and been able to build upwards of twenty destroyers instead of the three we managed to complete.