Now all countries tend to join together to make a big organization like EU. I wonder that in future, there are no longer small country. They are only EU, America, Australia, China, India, Russia. No more France, German...anymore. What will world be in future?
Its called cutting the 'cloth to suit the situation', its not a constant, and will always be subject to change re expanding a region/or a country, its all relevant to the political and financial rewards of uniting or/dividing and/or separating a region or country Money and Oil etc and assets are major factors
Why? Because Autralia like US before. It is in a continent isolate from other part of world. It is big enough to avoid any attack from others.