Early in the story of the Bible God focused His attention on one nation- the people of Israel. Though God was working with and through them, He still promised that they would be a blessing to all the peoples of the world. When Christ started the church He was very clear that His followers were to take His message of salvation to all the world- specifically to "all the ethnicities." The Christian church quickly expanded beyond it's Jewish origin and spread throughout the Roman empire. Throughout the centuries the gospel has continued to reach new groups of people.
God is very clear that His followers are to become one new group instead of remaining independent from each other. The night before Jesus went to the cross He instructed His disciples with these words: "By this all men will know that you are My disciples, if you have love for one another" (John 13:35). Thus, we are not to huddle only with Christians who look like us or who were raised like us. Our love for other believers who are different from us is an example to the world that we have truly been transformed by Jesus' power.
It is understandable why many churches are segregated. In some places I have lived it would be impossible to have a church composed of people from a variety of ethnic backgrounds simply because the populations of those areas were not diverse. But in other parts of our country and the world, it is scandalous that our churches are segregated based on racial features. Here in the heart of New Jersey I see people that look different from me and from each other everywhere I go. A church that welcomes all of these different ethnic groups is a church that displays God's love to the world.
Here is how one pair of authors stated the matter:
"For in an increasingly diverse and cynical society, people will no longer find credible the message of God's love for all people when it's preached from segregated churches."
What can we do? Very simply, make friends with people from other cultures, share the gospel with people from other cultures, and worship with people from other cultures. It may not be easy, but it is a very necessary way to display Christ's love to our world.