Distance is the only thing that divides the church. It is not divided by doctrine. While it is worldwide in reality, it is local in its expression. As we look back to the Bible, we see that Paul ordained elders in every church. Paul also told Titus in one place to ordain elders in every city. I think we can clearly see that the church's boundaries are a city or locality. The church government God has given meets the need within these boundaries. When we go further than that, we run into problems. If we have less than that, we have problems. So, we need God's order. We need to realize that God wants one expression of Himself in every city or locality.
Today, with cities being as large as they are, it may not be practical to have just one church in one city. But each locality should have one church, functioning autonomously under the headship of Christ. It is there so that believers may go and be fed as God has designed. It is not controlled by man, but God has ordained elders or overseers to watch out over and care for the people of the Lord who have been added to the church by the Spirit.