I for one would love that cos as it is I am a mess when it comes to origin and ancestry, what with each of parents, grandparents, and great parents all being of totally mixed parentage and origin.
One world with no borders would mean I can say in fact I am truly a citizen of planet earth, something I proclaim even now, but the difference would be I won't get any weird looks!
In any case we are all travelers in this world...would be great to identify ourselves as such and end all the nationality conflicts and patriotic boasting!

However that will not of course be a solution for all of the other trials and calamities that prevail amongst us today. In fact we can then expect a host of new ones cos man being man, will never be able to survive in complete peace and unity...troubles will still arise, crimes and oppression will continue even if we are all supposedly a part of one nation. Such is mankind!