"just what exactly would be wrong with one world government? One government with not one leader but more along a counsel. For starters each nation gets a vote but after that maybe we go to a representative system where the entire world is divided up into districts of 1 million people. That aught to be a small enough population to think in terms of global decisions. Each nation can maintain control of its property and each municipality can remain in control of their local area schools and courts and such." snip

IMHO, nothing... so long as it is not a totalitarian one. But it would have to be, I think, a bit on the authoritarian side. Probably should be an elective monarchy with the monarch-pool selected from small, historically peaceful and happy nations. (One SF novel I read had an appointed Queen from the Royal Line of Tonga.)