Why is the official name of the true church in the Bible "Church of Christ"?

Why are there so many 'Churches' mentioned in the Bible? :

"Church of Galatia" (Gal.1: 2)

"Church of Macedonia" (2 Cor.8: 1)

"Church of the Gentiles" (Romans 16:14)

"Church of God in Corinth" (1 Cor.1: 2)

"Church in Antioch" (Acts 13: 1)

"Church in Jerusalem" (Acts 8: 1)

And much more. All of this refers not to the whole Church established by Christ, but to the locals or places reached by the Church of Christ in the time of the apostles.

In fact, it is not appropriate to call the "CHURCH OF THE GENTILES" the Jews who became members of the Church. Likewise, it is not appropriate for the Church in Jerusalem to be called the "Church of Macedonia". But it is appropriate to call the members of the Church established by Christ wherever they are called the  Church of Christ (Romans 16:16).

Romans 16:16

"Greet one another with a holy kiss. All the churches of Christ send greetings."

the churches of Christ in Romans 16:16 is GENERALIZED in to all Churches. Why?
Paul the Apostle who wrote Romans, who called to everyone / to all churches - send greetings.
therefore it makes the scope in GENERAL thus It provides an 'official name'.

Name is important

Acts 4:12

Salvation is found in no one else, for there is no other name under heaven given to mankind by which we must be saved. 

Church of God or Church of Christ?

"Church of God."

"This term is used ten times in the New Testament, and its only use by Apostle Paul. It is important that he often used it when speaking to Gentile Christians.

Six of these instances are in the letter. Corinthians.

The Corinthian Christians were in the midst of other disgusting idolatry. They themselves, at first, were misled by the stupid idol. (1Cor.12: 2)

"They must now remember God as they are. He has appointed them ..."
(cf. The Church In The Bible, pp.349-350)

Remember: Before they became with God or the Church of God, firstly God ordered them to become in Christ or the CHURCH OF CHRIST..

Is it difficult to confirm if people are with God if they are not with Christ? the answer is obviously Yes. You can't be with God without the mediator - "Jesus Christ"

Living in the absence of God, the people who are separated from Christ, this is the situation of people before they became the body of Christ or Church of Christ

Ephesians 2:12

remember that at that time you were separate from Christ, excluded from citizenship in Israel and foreigners to the covenants of the promise, without hope and without God in the world.

So how can a man be with God if he is separated from Christ. The Bible says .. They used to live without God.

Who is with Christ? :

Members of the Body of Christ follow Christ as their Head (Ephesians 1:22-23).

22 And he put all things under his feet and gave him as head over all things to the church,

23 which is his body, the fullness of him who fills all in all.

Church of Christ :

Ephesians 5:31-32

31 For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh.

32 This is a profound mystery--but I am talking about Christ and the church.

Isn't that true that what God unites should not be separated?

Such is the mystery of Christ's relationship to the Church as compared to the husband and wife who became one FLESH.

So in order for a person to have a relationship with Christ and not be separated from him he must enter his body or his Church.

Because if a person is separate from Christ or his Church he lives without God in this world.

There is no Difference between Church of God or Church of Christ. :

John 17:9-10

9 I pray for them. I am not praying for the world, but for those you have given me, for they are yours.

10 And all Mine are Yours, and Yours are Mine, and I am glorified in them.

 ..And all Mine are Yours, and Yours are Mine,..

For God to be with you, you must be in the body of Christ or the Church of Christ.