I quoted Jesus himself denying his kingdom is from here which means he was not the King of Israel at that time. One day he will be, but not until he returns.
Jesus was rejected by the Jews at that time as their king of Israel.
You quoted Jesus as he was being interrogated by Pilate to see if there was any grounds to the accusation by the religious leaders that Jesus was planning an insurrection against the Roman control over Jerusalem.
John18:
29 Pilate then went out unto them, and said, What accusation bring ye against this man?
30 They answered and said unto him, If he were not a malefactor, we would not have delivered him up unto thee.
Jesus answered Pilate that he was not planning an insurrection.
36 Jesus answered, My kingdom is not of this world: if my kingdom were of this world, then would my servants fight, that I should not be delivered to the Jews: but now is my kingdom not from hence.
37 Pilate therefore said unto him, Art thou a king then? Jesus answered, Thou sayest that I am a king. To this end was I born, and for this cause came I into the world, that I should bear witness unto the truth. Every one that is of the truth heareth my voice.
Jesus was not saying that He was not the messiah, whom God had sent to be the King of Israel, in those verses. Jesus told Pilate, that his kingdom was not of this world - i.e. meaning that Jesus's kingdom was the kingdom of Heaven.
Pilate then in verse 39, told the Jews that he found no fault in Jesus regarding the accusations that Jesus was planning a insurrection of the Roman rule.
Pilate in the same verse referred to Jesus as the King of the Jews.
Pilate aknowledged that Jesus was the King of the Jews - do you ?