Yes, Australia is a nation-state.
No, Australia has not been sold to the United Nations. The idea that a country can be sold is a misconception; nations are sovereign entities and cannot be bought or sold like property. Australia is a member state of the United Nations and participates in various international agreements and organizations, but it retains full sovereignty over its territory and governance.
Australia is a federal parliamentary democracy, and a commonwealth realm of the British Commonwealth of Nations; it is not within any other state. the name of the country is also the name of the continent it occupies.
Antarctica has no nations. Australia is one nation.
England and Australia are separate jurisdictions, although Australia remains part of the British Commonwealth of Nations, and Queen Elizabeth II is the official head of state of Australia. But the position is ceremonial only.
Australia
United Nations Association of Australia was created in 1945.
Australia has the fewest nations.
Bermuda, Bahamas, Jamaica, Australia, Canada, New Zealand
Australia
Yes, both Australia and New Zealand are members of the Commonwealth of Nations.
The Commonwealth of Australia is a self-governing nation.
Australia's largest state: Western Australia. Australia's smallest state: Tasmania