They are though. The USA is a collection of former independent states. Germany was formerly Prussia plus many city states up until 1815, the Italy of today was formerly a collection of independent states until 1856. Nations uniting, have happened throughout history. Poland and Lithuania, Austria and Hungary etcetera, to name a few, and will continue in the future.
The EU, Latin American Free Trade Association, ASEAN Free Trade Area, the African Union are all "Free Trade Bodies" that may very well unite to form a nation such is the way the world is going.
Cooperation and fairness is the key.