The US Airborne expansion gives you Player Soldiers, Non-Player Soldiers, and Squad Soldiers from the United States Airborne. Also included are their Weapon and Equipment cards.
This provides you with everything you need to run missions.
All you need to do is substitute these Soldier, Weapon, and Equipment cards instead of the regular US cards at the start of a Mission, and you are good to go.
Also includes more Mission and Objective cards!