Answer: The same Bible verse also says in Christ there is neither male nor female, yet most people don't claim that it abolishes human sex. The existence of human males and females is biological reality just as existence of various nations and ethnic groups. The verse deals with spiritual, not biological reality. Anyone can come to Christ if he chooses. Further on, there is a story in Genesis about Tower of Babel:
6 And the LORD said, Behold, the people is one, and they have all one language; and this they begin to do: and now nothing will be restrained from them, which they have imagined to do.
7 Go to, let us go down, and there confound their language, that they may not understand one another's speech.
8 So the LORD scattered them abroad from thence upon the face of all the earth: and they left off to build the city.
According to the Bible, it was God's will that mankind stays divided.
Claim: The Tower of Babel was in OT. NT has a story of Pentecost. It means that national borders are wrong and should be abolished and all nations should be united in one.
Answer: Read the passage from the Acts describing Pentecost:
And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
6 Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them speak in his own language.
7 And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans?
The apostles were speaking in different languages so that believers from many nations could understand their message. Languages weren't abolished and neither national distinctions. National divisions will persist in eternity:
24 And the nations of them which are saved shall walk in the light of it: and the kings of the earth do bring their glory and honour into it.
Whether you are a believer or not, one thing is clear: the Scriptures don't teach the New World Order or one world government or any such thing. In fact, they do point out that when mankind is united, naughty things start happening.