Coincidentally, after my previous post in this thread, I happened to watch These Final Hours. For those who haven't seen it, it is a recent Australiian movie set in Perth during the end of the world due to (what I deduced was) a comet having impacted Earth in the North Atlantic. As the ripple of fire and brimstone inexorably races towards the city, the movie portrayed people turning on each other and satisfying their basic instincts, with life and the law rapidly losing all value (though the main protagonist tries to redeem himself by helping a little girl reunite with her father).
When you recall what occurred after Hurricane Katrina in Louisana less than a decade ago, it is not hard to imagine this scenario unfolding as the thin veneer of civilisation is stripped away and it can be a bit depressing. Of course, if there had been a chance to stop the comet from hitting the planet through a united global effort, it might have been a more optimistic film.
While I have faith in human beings on average, I think we have a way to go before we evolve beyond our primitive tribal (nationalistic) instincts.