A passport is
an official document issued by the government of a country to one of its citizens and, varying from country to country, authorizing travel to foreign countries and authenticating the bearer's identity, citizenship, right to protection while abroad, and right to reenter his or her native country.
anything that ensures admission or acceptance: A good education can be your passport to success.
any authorization to pass or go somewhere.
a document issued to a ship, especially to a neutral merchant ship in time of war, granting or requesting permission to proceed without molestation in certain waters.
a certificate intended to secure admission.
A passport in the sense we intend to use it is meant to be an international document. You don't need a passport to move withing a country. Adding 'international' to it then makes it redundant and superfluous.
That is English for you.