As adjectives the difference between international and united
is that
international is of or having to do with more than one nation while
united is joined into a single entity.
As proper nouns the difference between international and united
is that
international is international Airport, as the shortened form of an airport name while
United is any of many football teams formed by the amalgamation of smaller ones.
As a noun international
is someone who has represented their country in a particularly sport.
As a verb united is
past tense of unite.