I believe Niue is the smallest Self Governing country.
Self-Autonmy
Commonwealth
Canada joined the Commonwealth after it became self-governing.
Puerto Rico is an unincorporated, self-governing territory of the United States and styles itself ( in English) as the Commonwealth of Puerto Rico. Its name in Spanish, Estado Libre Asociado de Puerto Rico, is more literally translated to English as "Free Associated State of Puerto Rico."
A state is a fully self-governing political entity within a country, with its own government and constitution. A territory is an area controlled by a country but does not have the same level of self-governance as a state.
Denmark has two self-governing possessions.
Self-Autonmy
Denmark
Yes.
Domninion
Australia is both the smallest continent and a self-contained country.
Commonwealth
1867
Greenland is a part of Denmark.
Commonwealth
Japan is an independent, self-governing nation.
Russia is a self-governing sovereign nation.