alternatehistory.com

Federation of the colonies is only partly successful: neither New South Wales nor Western Australia can be brought round to agree to become part of the Federation. No matter how many referenda are held, the answer is still consistently "No". So eventually, the Commonwealth of Eastern Australia is formed consisting of Victoria, Tasmania, South Australia and Queensland (including the Northern Territory as well). Eventually New South Wales gets an upgrade from colony to dominion as well, but still separate from the Commonwealth. WA stays a colony.

So, what happens then?
Top