If Jason Johnson was a returned LDS (Mormon) missionary, then he was incorrectly dressed with his vest. He would wear brown T-Shirt like underclothing.
Jason refers to his gunnery sergeant as sergeant. In the U.S. Marine Corps all sergeant ranks are addressed by the actual rank they are. Therefore, Jason should've referred to him as "gunnery sergeant" or "gunney."
Early in the film Jason says he's up for a promotion. Later, he tells Meriam he was promoted again. He answers the phone identifying his rank as lance corporal when Meriam calls him to tell him she can't see him anymore. On the roof at the Mannai Plaza he's already wearing the lance corporal insignia. It he was "promoted again" he'd be a corporal.
Mountains can be seen in background, there are no mountains in Bahrain.