Just thinking in very broad outlines here: it'll probably help if Australia and New Zealand are united. Something that is still recognisably 'like' moder Australia could become much more imperial if we could have:
- no Meiji
- no Japanese involvement in WWI (or equivalent - or maybe just no WWI)
- a slower decline or fragmentation of the British Empire, with colonial mindsets remaining acceptable for longer.
Australia, a white Dominion with support from London both militarily and financially, could easily take over Britain's interests in the Pacific and bits of Southeast Asia. If India devolves, it may be considered preferable for Malaysia to end up in Australia's sphere of influence rather than India's. With that position, the other European colonial powers will end up seeing their holdings (Indonesia, New Guinea, Melanesian and Polynesian islands) slip into its ambit. Quite possibly, this Australia would also pursue maritime interests in continental Southeast Asia, 'protect' Hong Kong, or otherwise acquire interests in China.
With this setup, Australia would maintain a large navy and professional army and charge an 'empire premium' to keep the peace in its backyard. In effect, it would treat the western Pacific the way the USA historically have treated Central America. If there is a strong US presence in the region, it would function as an ally. If not, it could effectively fill the vacuum and even inherit the Philippines and Hawaii. The wealth thus generated, combined with Australia's ample resources, could easily justify spealing of a 'land of plewnty'. Imagine a comprehensive welfare state underpinned by a racial ideology, where white Australians are assured of a basic first-world standard of living and veterans of the Empire given pensions, education benefits and plum jobs in governmernt and industry. Heavy defense spending supports the system (veterans are given preferential employment in the navy yards, arms factories, and government departments). The Australia ideology would emphasise healthy outdoorsmanship, athletic prowess, scientific learning and racial pride.