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

Team	How to unlock
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