While I'm generally down with remaking films where the original left room for improvement - and, certainly, John Milius's mid-80's concoction of rampant, Reaganite paranoia, left a lot of that - the idea of a foreign power invading the Unites States is not really one which has improved with time, not least due to the collapse of the Soviet Union, since they were probably the sole semi-credible candidate. Yes, as the intro points out, North Korea may have the 4th-largest army in thw world. But guess who's #2, and has a vast technological advantage to boot? Even if, as the film suggests, an EMP weapon is used to disable military infrastructure - though not, it would appear, doing enough damage to stop Subway(TM) sandwich shops from functioning as normal - America has enough firepower roaming the globe to reduce Pyongyang to a pile of glowing rubble, and be home in time for tea. [It was originally supposed to be China, which might have worked better; that idea was scrapped because MGM wanted to release the film there!] Suspending my disbelief regarding the basic premise is tough enough; when the Russian spetsnaz then show up to help the Koreans, is I think when my interest formally checked out.
There was certainly nothing among the characters to retain it. You have the adequate Hemsworth, playing a square-jawed marine, who bickers with his brother (Peck) as, along with a group of high-school kids who might as well have interchangeable heads, personalities and dialogue, they form a resistance movement against the occupying forces, who have taken over their North-West town because... Er, not quite sure, actually, why any invading force would give a damn about Spokane. The sole saving grace is the action, with veteran stunt co-ordinator and second-unit director Bradley handles with the benefit of much experience. Fortunately, there is enough of this to stop the film from being actively boring (if that isn't a contradiction in terms), and if you are doing something else with this in the background, it would likely be okay. However, as someone whose reaction to an invasion would probably be, "I, for one, welcome our new North Korean overlords," there isn't enough to overcome my inherent cynicism regarding the core concept.