There's a scene in this movie where Chuck Norris' character says "I'm gonna hit you with so many rights, you're gonna beg for a left." with a completely straight face. If that doesn't make you smile, you're not the right audience for this movie. It has an interesting premise, albeit a mostly squandered one. Squads of terrorists infiltrate America, and disguise themselves as police officers, guards, soldiers- etc, and then set out on a campaign of chaos and carnage. Thus... effectively turning the American people against their own protectors. This movie could never be more cultural relevant than right now, except it never will be because the movie doesn't do much with this concept and it devolves into Chuck Norris vs. several hundred of stock bad guys.
