I think that it is generally because history has shown that a consolidation of power into just a few hands is almost always a bad thing. A one world government would be the epitome of that.
where has history shown that? if anything, history has shown that as the world has become smaller via transportation and communication the government can become less spread out.
hmmm... the Soviet Union??? But , i guess killing a dozen or so million citizens (Ukraine) isn't a big deal. You just confirmed how ignorant you really are.
What about the Union of American States? It's the same population. What bad things happened with that? Are our historical mistakes (slavery, Native American mistreatment) due to federalism and consolidated government of states?
Or how about the European Union? It's even more populous and almost as diverse as the USSR. What's bad about that? Serious question. Seems like a bunch of folks have actually wanted to be in the EU.
Was the Indian Partition a good thing, then? A million died at the time. Why?
What about when Italy was unified in 1861? Problematic?
I'm not sure "history has shown" anything of the sort being asserted here...