Wikipedia, which I would not consider to be significantly reliable would tell us there are over 41,000 "Christian Denominations." You might be saying the same thing I said when I read that; that is, there is no way! And although I wish it weren't the case, I don't have any proof that Wikipedia is incorrect in this matter. Despite what ever the exact number of churches may be, the fact of the matter is: If there is more than one that is too many! If there were two churches in the world that claimed to be Christian, that would be one too many. The reality of this matter is that God and Jesus intended for there to be one church, His church.
Jesus said on one occasion that, I will build My church and the gates of Hades shall not prevail against it (Mat. 16:18). That denies all speculation that might be made. In John 15, Jesus spoke concerning His disciples (what would be the church) that, I am the vine and ye are the branches. Did this mean that Jesus was the vine and the many branches were the different "Christian Denominations" in the world? No, certainly not because that would mean there was a contradiction with what Jesus said previously in Matthew 16. Additionally it would mean a contradiction between Jesus the Lord and Paul the apostle. Paul said in Eph. 4:4, There is one body. Consider also Paul's words in Eph. 1:22-23, And hath put all things under his feet, and gave him to be the head over all things to the church, Which is his body, the fulness of him that filleth all in all. Combining what Jesus said and what Paul said, knowing that the Bible is from God and contains no contradiction, but rather passages that complement, we have a complete thought. Jesus built His church, of which He is the head, which is His body.
What a blessing it is to have God lay bare the things concerning His church. We don't have to worry about not understanding what the role of the church is in our lives, we don't have to worry about not understanding how to enter the church; He has left it open for us to view. Acts 2 teaches that the saved are added to the church (v. 47). In order to be added to that church we must be obedient to His word. We must hear the word (Romans 10:17), we must believe that Jesus is the Son of God (John 8:24), we must confess that belief with our mouths (Romans 10:9-10), we must repent of sins (Acts 17:30), and we must be baptized into Christ (Gal. 3:26-27; Col 2:12; 1 Pet. 3:21).
We can have religious unity in a world of division because the conditions for salvation and addition to the church have remained the same since the time they were first preached. Our responsibility is to take what God has laid bare and open for us to know and to do it and teach it. May God bless us with unity in this world so that His work is done to the effect that He desires. To God be the glory!