A sovereign state, or nation of any kind, is a unit that provides identity to its people economically, socially, culturally, religiously and, if not artificially formed, to a considerable extent represents the people and the preferences of those people within that state or nation. Even in the case of the worst dictatorship or the worst tyranny within a nation this remains true by virtue of the nature of the leadership either having evolved, or having been allowed to evolve or gain power by the people within that state. One of the features of a nation state is that geographically it has coherence and will occupy an area that has evolved based upon the prevalent factors including all of the above, plus practicalities of communications and defence etc.
The converse of the nation state is the superstate. By its very nature the superstate is not likely to be democratic, because it is governed by a body that has presumed to represent and rule over peoples of different races, cultures, economies, geographical types and different natural industries to the nations contained within it.
The most perverse of superstates may not yet have been seen in full but are thought to be in the making, one of the most extreme of which is the so called European Union. Even worse than the superstate would be a situation in which a single government ruled over the entire world. In the latter one world tyranny from which there could never be any hope whatsoever of escape, the final demise of the human race would be assured whatever form and route it took.
Indeed, the final demise of the human race in such a situation could in fact take place very quickly. As seen in the United States of America in the 19thC., to simply end slavery in one part of the country, the whole country became engulfed in a particularly nasty, hard fought civil war the likes of which have rarely been seen, and may only have been equalled or surpassed by the civil war that took place in Russia in the early 20th C. The unaccountability of any sort of any ruling body in such a world would be absolutely minimal if not quite non existent.