An article in Foreign Policy notes that we're woefully unprepared for a space alien invasion:
[T]here's one thing that unites Americans: Our shared fear of an alien attack. They also remind us that when the invading space fleet arrives, humanity is not going to surrender without a fight to our intergalactic invaders. Instead, we will band together to fight off their incredibly advanced weaponry with our ... well, with what, exactly? Are we really ready to battle our would-be alien overlords?
With the Global Warming Apocalypse looming, we sure don't need another threat the planet earth.