I think that it is not only feasible, but necessary that the world become united under a single world government. Does this mean that there would be no borders? There are many nations which are divided into provinces, states, counties, and other smaller areas under local governments, so why would there not continue to be national governments under a federation of nations?
Though the creation of a world federation of nations is an important step in the maturity of human kind, other, more fundamental questions must be answered.
First of all, what is going to motivate the governments of all the nations of the world to take the step of subordinating their rule to the world federation? One would hope that it is will of the people to form such a union. (And I don’t mean people whose wills have been manipulated by sophisticated propaganda paid for by a conspiracy of corporations run by power-hungry sociopaths!)
And what would motivate the people to want to form such a union? More importantly, what would influence people to strive to eliminate prejudice from their own hearts, and to raise a generation that was free of prejudice? Also, what might motivate and inspire people to take a chance that a world in which people all worked towards the common good might be a better world for everyonethan a world in which those who could pursued their own interests despite the disruption of the common good? For such a "cultural and economic Utopia" to function, the governments at all levels would need to make their decisions based on what they honestly thought would be best for all the people on Earth, not just for the people of their city, county, state, or nation. There would also need to be a system whereby everybody could offer ideas for improving things and know that their leaders would listen.
The answers to these issues are not going to be resolved through legislation, politics, or manipulation. It is really a matter of influencing and responding to people’s hearts and minds at the same time.