Well, usually it will happen that you will have those fighters on US carriers, even without wanting to use it in this way. If Australia can earn around 15 - and usually that is what they can get until Japan is taking care of islands, India, China, Russia - they will buy a fighter every round or two. In order to be able to invest both in Europe and Asia, US can save some money by buying a fighter less. Effectively, if they buy a carrier and wait for two rounds, they are getting excellent defending power for 16 IPC.
With those ANZAC fighters sitting on the US carriers, it is then opportunism - let them sit back near Australia coast and if an opportunity arises, go kill those transports.