What we should have is a one world "community" or a one world "system" but not a one world "government" or one world "nation" because a nation is an obsolete notion in the first place if everyone in the world is in the same system and there are no separate nations and the existence of a government is impossible for a society which is enlightened enough to sustainably maintain civilization on a global scale without descending back into separation through physical warfare, disputes over land and resources and cultural/ideological differences. For any type of global socioeconomic system to exist, human culture would have to change drastically and universally, all of the social constructs of the old society such as the monetary system and the entire notion of "politics" within it's current context would have to be replaced because the entire psychology and consciousness of humanity would have to be changed in order to accommodate a vastly more complex and symbiotic environment. To make a long story short, we will always have wars, cultural conflicts and separate nations until a new standard and a new norm of human awareness is reached which allows us to move out of the range of susceptability to institutions, social constructs and superstition because the unscientific approach of a type 0 civilization is inadequate when you are dealing with the prospect of making the resources and the ecosystem and the technologically advanced civilization of an entire planet all work symbiotically and mutually enhancing all of those systems as opposed to destroying the environment and engaging in wars with each other as we currently do.
Unless of course you are hoping for a technocratic dictatorship where humanity will be driven to extinction by our immortal AI overlords, there are more than one kind of "globalism" obviously, there mutually beneficial forms and mutually destructive forms, the kind of "global system" I described is substantially different from the lesser and more commonly reffered to forms of globalism like corporate globalism and multinational Rothschild banking cartel globalism, these forms of globalism along with the idea of a global government have the potential to drive the human race to extinction, so needless to say they wouldn't be very sustainable in the long run. Except for the AI overlords that replace the human race.