In order to unlock the 7 classic national teams in the game
you must win the International Cup with their current counterparts. 

Classic Argentina   - Win the International Cup with Argentina.
Classic Brazil      - Win the International Cup with Brazil.
Classic England     - Win the International Cup with England.
Classic France      - Win the International Cup with France.
Classic Germany     - Win the International Cup with Germany.
Classic Italy       - Win the International Cup with Italy.
Classic Netherlands - Win the International Cup with the Netherlands.