Man must be dispersed in order to develop individually. There is a real spiritual basis for the need for cultural pluralism, including different and somewhat mutually incomprehensible languages. In this context, one nation can arise slowly, over a long period of education, trial, and redemption, which will carry on God's message for humanity. Within Nimrod's Bavel, Judaism is impossible. Within any world order, world empire, Judaism cannot arise.
Mankind is dispersed to develop individual character, cultural diversity.
In one corner, without having to worry about the destiny of all mankind, a small family will build the kingdom of God. Cross-cultural dissonance is the price that must be paid for spiritual development. In Avraham's case, that dissonance will be even more extreme. Only through lonely separation can true spiritual greatness be achieved. The unity of the Jewish people will be achieved through that spiritual development, slowly over many generations, with the Torah and Eretz Yisrael at its center.