I would have to rate this movie as an artistic statement about political and social priorities. In real life, right now we have the technology to detect and deflect world killing comments, not through something flashy like nukes and bombs, but by detecting threats when they are years out and sending ion satellites to provide a gentle nudge, altering the trajectory over hundreds of millions of miles. The cost for such a system is under 10 million, which is almost nothing in terms of governmental spending.
So has it been created, is it ready to deploy... NO... why because forwarding the paltry sum of funds to this sort of project has absolutely no impact on becoming re-elected, it isn't sexy or interesting. There is also a very good chance that such a comet strike will not happen in the next 1000 years, (just as much as finding it tomorrow) so why take political heat for such a proposal??? Deflection of world killing comets can only happen when it ISN'T an emergency... of course such a system would mean that it never becomes an emergency, no one in our society will even notice about a rock that fails to hit our planet... no glory. It is like treating a wound with penicillin rather than leaving it means the amputation never would be needed. A prevented emergency is a non-event.
Perhaps that is the message behind this movie. If so it delivers something to think about. Enjoyable? Happy? Feel good flick? Not really, unless you like the