Under Covenant, Christ was sent to earth to be the king of the Jews.
Matthew 2:2 Saying, Where is he that is born King of the Jews? for we have seen his star in the east, and are come to worship him.
Under Grace, Christ is no longer operating as king of the Jews but rather the HEAD of the church which is his body,
Ephesians 1:22 And hath put all things under his feet, and gave him to be the head over all things to the church,
Ephesians 5:23 For the husband is the head of the wife, even as Christ is the head of the church: and he is the saviour of the body.
Colossians 1:18 And he is the head of the body, the church: who is the beginning, the firstborn from the dead; that in all things he might have the preeminence.
Most of us have sang the songs, heard the sermons and bought the bumper sticker proclaiming Christ as our king. However, the bible says to "Prove all things; hold fast that which is good." (1 Thessalonians 5:21). We're to do that by God's word of truth rightly divided and not by man's conjecture through years of tradition.
In time-past Christ was King of the Jews, but currently operates as "head of the church".
While we certainly recognize that the Lord Jesus Christ is the "King of kings" (1 Timothy 6:15) and "King eternal, immortal, invisible" (1 Timothy 1:17), we must also recognize that he is not exercising his kingship dominion according to this present dispensation of grace.
However, "in his times he shall shew, who is the blessed and only Potentate, the King of kings,..." (1 Timothy 6:15).
A King needs a kingdom and is what was offered TO and rejected BY the nation Israel. In the future they will accept him as their King during the millennial reign. At that time, Christ will have dominion here on earth.
But presently it is Satan who is the "prince of the power of the air" (Ephesians 2:2). He is "the god of this world" (2 Corinthians 4:4).
In lieu of his physical absence, Christ is the head of the church which is his body here on earth.
"Not being known doesn't stop the truth from being true."