How to unite the world in less then thirty minutes:

WAR (sorry George Lucas)! We quarrel on resources, ideals, beliefs.. you name it. Instead of working together, we're in a downward spiral of conflicts, terrorism and global exploitation that has steadily escalated in the past decade. Then you ask, is there not a suitable resolution to end to this cycle? Then here's the answer:

Extra Terrestrial Calamity + The human race = Global Unity

We need some alien race, hell-bent in ending our world, so that can we look into each other's eyes, hold hands and battle it out for a common cause, survival, you know just like Starcraft. Until then, we'll be caught up in our own tentacles, become extinct, allowing the raccoons to finally evolve and colonize mars. They'd probably plonk a flag on the surface engraved with a middle finger paw exclaiming, "I won suckers!"