The Tower of Babel…

When man worked together after the flood, their first communal act was to unite against God. Mankind was punished by God with different languages (and probably ideologies). Therefore, they were prevented from staying united. This caused the birth of nationalism, which is still with us today. It should be noted that Jesus ministry and resurrection rectified this a few ways:

1.) Jesus preached to and about Samaritans in a positive way even though they were prejudiced against each other at the time.
2.) Philip converted an Ethiopian (Acts 8). Peter converted a Roman, Cornelius in (Acts 10).
3.) Christians were gifted with speaking in tongues, which completely corrects for Babel in the early Christians ministry.

As long as man rejects God, they cannot be united. True Christians will know each other by exercising of John 13:35 - "By this everyone will know that you are my disciples, if you love one another." [regardless of race or other differences]