Tribalism was a problem in New Testament times. Although the universality of the gospel seems obvious to us, it took the early Christians years to realize that the message of salvation wasn’t just for Jews. Then they shared it with Samaritans, since they already believed in the same God, practiced circumcision, and held to a very similar religion. It took divine intervention to get the early disciples to share the gospel with non-believers, and even then, some weren’t too happy about it.
In Acts 11, we see that the believers were scattered from Jerusalem and went out spreading the good news… to Jews. Over time, some came to share the message with Greeks, and many non-Jews were converted. The church in Antioch was one of the first integrated churches. The people around this church came to realize that this was not just another Jewish sect, yet it wasn’t one of the Greek mystery religions either. Astonished at the disappearance of tribalism, the citizens of Antioch had to invent a new term for these disciples: Christians.
When Christians overcome the barriers created by man, the world takes notice.