It gains a second star because it is semi-exciting with the talented sniping shown. However the talents are also ridiculously exaggerated.
The major flaw of the movie is the complete worthlessness the main character displays. For being a supposed trained specialist not once does he do anything to improve his own situation. He is reactionary and dumb and accepts his situation rather than fight. Not at all what a trained fighter would do. He is a simple sheep waiting for slaughter.
The only intriguing aspect of the movie is the dialogue between the enemy snipers. Yet even in that the main character is constantly worthless. All conversations from the enemy sniper are used to bait and setup the main character, and yet somehow he never realizes any of this.
If you want to watch a movie where the American military is dumb and helpless, then this is the movie for you. Otherwise save the time and know John Cena yes does die.