Continuity mistake: When the main character goes to visit his friend that had been shot in Iraq, they're driving down a country road in a 2 door Dodge Challenger, but when inside the vehicle it's a Dodge Charger, which is a four door car.
Factual error: M60A3 tanks and AH-1 were no longer in service at the time of the invasion in 2003, replaced by the M1 Abrams. The AH-64 humvees have crew protection that did not exist prior to 2005.
Factual error: In a picture from the UN headquarters in New York in the year 2003 you see two German flags. The German Democrativ Republic hasn't existed since 1990. (01:16:04)
Factual error: Before and during the Marines' arrival in Marjah, some of them are wearing Dust Goggles. These would've been first issued in World War II and continued into the early 2000s. The Battle for Marjah took place in 2010, by which point these goggles had been replaced by superior models such as ESS for some time.
Continuity mistake: When Megan is outside the supermarket asking people to sign her petition, a woman walks up and begins writing on the clipboard. In the first shot, the cap is on the back side of the pen. From the next angle, the woman is scribbling and lifts the pen to show the cap covering the tip that she was "writing" with.
Revealing mistake: Right at the beginning of the movie, an alien blasts Lieutenant Smalls and he drops his rifle. The weapon wobbles, revealing it's a rubber prop rifle. (00:01:55)