What is the difference between an island and a continent? Why aren't Africa, Europe and Asia considered a giant island? I believe that opinion is divided about whether Australia is one or the other. If it's a continent, it's the only single-country one, although Western Australia came close to seceeding in the 30s.
I think it is a question of whether it dominates a continental plate or not? There are sometimes references to "Afroeurasia", but they are usually considered to be continents who are currently, but temporarily (in the long term sense of the history of the planet) joined together.
Western Oz seceding? That is a new one on me, my understanding is that Western Oz is the City of Perth,and what a female backpacker described to me as "Thousands of miles of bumfuck nothing".