This Australian take on Red Dawn is based on the first of a long-running series of books, and that might be part of the problem. While it covers more or less the same ground - teenagers find their town has been invaded, and fight back, beginning a guerilla campaign against the occupying forces. Here, unfortunately, the emphasis is very much on "beginning". By the end of the movie, they've really only carried out one such action, and the film ends, just when you feel it should be getting going. Rather than a self-contained entity, in tone and content it feels more like a pilot episode for a television series. That's a dangerous tack, unless you can bank on future episodes, e.g. if you're adapting Frodo Potter and the Twilight Hunger, or some similar blockbuster.
While this did okay on its home turf, the relatively large budget meant it needed to do well overseas as well, and a failure to do so renders the prospect of any closure severely uncertain. Which is something of a shame, as there are some decent aspects to this. The character are, I sense, much less irritating than their American counterparts would be. While they are still quickly-drawn to the point of stereotype, e.g. the sensitive Asian kid whose parents run a restaurant, the rich bimbo who doesn't know snakes can swim [ok, I might have had to think about that too. In neither the UK nor Arizona, is this really an issue...], they come across as people it might not suck to spend time with. The action sequences are also well-handled and nicely physical, in particular one where a mechanical digger is being pursued by buggys. But it spends too long getting to that point, and ends up an unfinished cinematic symphony.