Factual error: At the Western Front camp near Washington, you can see tanks moving with their cannons raised to the highest angle. In reality, tanks move with their cannons in a horizontal position. The cannon is raised only when it needs to hit a high target, such as a high floor of a building.
Audio problem: When inside Washington D.C. and the AH-64 is firing its gun, the sound is completely wrong. In the movie, it sounds like a laser gun, and in reality, it's a M230 chain gun, which sounds different.
Unnamed Soldier: What kind of American are you?