One World Government

I spend a lot of time these days pondering the efficacy of establishing a single world government to oversee human matters. On one hand, it seems that a massive, coordinated effort is all that will bring about the necessary purpose and change to develop a plan that will need to encompass the entire planet. But on the other, great things have been done, with cooperation between disparate sovereign nations, for centuries. A worldwide communications structure now spans the Earth and the Heavens. A travel network allows one to arrive safely on the other side of the world within a day. Information is spread, ideas shared, and situations resolved all without a worldwide governance body.
But can this last?
I say no. Yes, the world can continue in its way for years to come, perhaps even centuries. And perhaps, we will get off this rock and out among the stars. But why hamper the process with political conflicts, non-standardized technology, disparate plans and the like? What is the real fear behind a World Governmental Body?
Some will say it is a futile effort - just look at the corruption and inefficiency of the UN. The inability to maintain peace and stability tells greatly against such a plan. But the thing that will truly bring about change is not a peaceful, happy coalition of countries working together. The only thing that might bind the nations of the Earth together is war. Conquest and ruin on a scale previously unimaginable. A squashing of each and every nationstate, subjugated to the will of the One Government. Only then, can standards be enforced. Resources used towards specific, humankind-spanning projects. But! The argument goes, large government is inefficient and wasteful. Full of corruption. Oppression for the sake of the few. And all these charges are correct, and all of these things will happen.
But at the end, after perhaps decades or even longer, the human spirit will rise and transform the oppression into benevolence. The egregious into the just. But only by travelling through this fire will humankind be forged into something greater, a dedicated race to colonize the galaxy that we live in. Only the full focus of our will and resources will get us off this rock. Are hundreds of years of ruin and tragedy worth the final price?