Factual error: When Blonsky is seen wearing the American Class A uniform, it's visible he has not shaved his face for days. Quite unthinkable for the military - be it American or British. If he had time to change from his BDUs to the Class A uniform then he would have had time to shave as well. Soldiers in Iraq aren't even excused from shaving daily unless they have a medical condition that prevents them from shaving.
Factual error: All of the soldiers in the movie are wearing the Battle Dress Uniform, but at the time the movie took place (around the same time as the first Iron Man) that uniform was already phased out and replaced with the Army Combat Uniform. Also, all of the soldiers had their name tags on the left side of the uniform, where the U.S. Army tag is supposed to go, instead of on the right side.
Factual error: General Ross and Blonsky are shown in their Class A uniforms, and both of them are missing their U.S. insignia on the collars. Also, General Ross is shown wearing the infantry cross rifles branch insignia on his collar, but as a general officer he would not wear a branch insignia. I could give Blonsky a pass since he's a British officer wearing an American dress uniform for reasons not explained onscreen, but Ross should have known much better as a general with decades of service.
Factual error: When Bruce and Betty are attempting to drive into New York, they get stopped at a police roadblock at the tunnel entrance and start walking instead. When we see them crossing a bridge, a sign says "No Wake - Speed Limit 9km\H. Being in the United States, this would be miles per hour or knots, not kilometers.