The kingdom of God is not a political geographical location drawn by arbitrary lines of men.
"20 And when he was demanded of the Pharisees, when the kingdom of God should come, he answered them and said, The kingdom of God cometh not with observation:
21 Neither shall they say, Lo here! or, lo there! for, behold, the kingdom of God is within you." (Luke 17:20-21, KJV)
And, future tense verbs written almost 2,000 years ago are not still future to us. The Olivet discourse told the time that the establishment of the kingdom would be in full force when the temple in Jerusalem was destroyed. That temple was still standing when Christ told His disciples that it would be destroyed, so the verb tenses used in that prophesy were still in their future. As the temple was destroyed in AD 70 the prophesy is not still in our future.
"34 Verily I say unto you, This generation shall not pass, till all these things be fulfilled. 35 Heaven and earth shall pass away, but my words shall not pass away." (Matt. 24:35-35, KJV)
"This generation" was their generation of the 1st century AD - not ours. Heaven and earth was a metaphor which the Jews used when speaking of the temple. So paraphrase vs. 35 and hear "The temple shall pass away...". It was also used by God to speak of the old and the new covenants.
"I call heaven and earth to witness against you this day..." (Deu. 4:26, KJV)
What did Moses say would be used to witness against, or judge the wicked? "Heaven and earth" was the law handed down in Exodus, the old covenant, the Mosaic covenant.
"15 And ye shall leave your name for a curse unto my chosen: for the Lord God shall slay thee, and call his servants by another name:
16 That he who blesseth himself in the earth shall bless himself in the God of truth; and he that sweareth in the earth shall swear by the God of truth; because the former troubles are forgotten, and because they are hid from mine eyes.
17 For, behold, I create new heavens and a new earth: and the former shall not be remembered, nor come into mind." (Isa. 65: 15-17, KJV)
The new heavens and the new earth, as opposed to the old heavens and earth, the old covenant then were the new covenant under the gospel of Christ.
So, Jesus told them in His Olivet discourse when He was coming with His kingdom, and that would be when the temple in Jerusalem was going to be destroyed, completely torn down.
"20 And when ye shall see Jerusalem compassed with armies, then know that the desolation thereof is nigh.....
31 So likewise ye, when ye see these things come to pass, know ye that the kingdom of God is nigh at hand. 32 Verily I say unto you, This generation shall not pass away, till all be fulfilled." (Luke 21: 20, 31-32, KJV)
Jesus told them the kingdom was near when they saw Jerusalem surrounded with armies.
"21 Jesus saith unto her, Woman, believe me, the hour cometh, when ye shall neither in this mountain, nor yet at Jerusalem, worship the Father.
22 Ye worship ye know not what: we know what we worship: for salvation is of the Jews.
23 But the hour cometh, and now is, when the true worshippers shall worship the Father in spirit and in truth: for the Father seeketh such to worship him." (John 4:21-23, KJV)
"And now is"... current and present tense while Jesus was standing with the woman at the well. Worshiping in spirit and in truth does not require a geographical location.
As Revelation was John's Olivet discourse, written in much Hebraic symbolism and metaphor about the destruction of Jerusalem - "that great city" - then seeing "the new heaven and new earth coming down out of heaven" was an event that happened after the temple in Jerusalem was destroyed.
"And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.
2 And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.
3 And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God." (Rev. 21:1-3, KJV)
The new heaven and earth covenant - the gospel of Christ. The "first heaven and the first earth" being old covenant, the old Mosaic covenant were gone when the temple was destroyed in AD 70. Thereafter the new Jerusalem, adorned as a bride was / is Christ's assembly, the body of Christ, the church of Christ. All who are in His assembly are in His kingdom and have been ever since that temple was torn down.
"No more sea" means no more gentiles. The sea was a metaphor for all the pagan nations that surrounded the "promised land" of Israel. They were called "floods" in the OT which God used to judge Israel and destroy the wicked (Isa. 59:19; Jer. 46:8). Paul told them there were no more Jew nor Greek (Gal. 3:28; Col. 3:11), that all who are in Christ are counted for the seed of Abraham (Gal. 3:29), then all who are in Christ are the true Israel of God no matter where they live, or are located on this earth realm.
The kingdom of God does not have a political, geographical location. It is made up of all of His saints in His body, who are tabernacling with Him, which recalls the last feast, THE feast of tabernacles / booths, also called the Feast of Nations. It represented the gathering of all of the faithful of God from all of the nations of the earth, no matter when or where we are - whether present in our mortal bodies, or having all already crossed over to our immortal abode in heaven.
As all those in Christ are the Israel of God, and as the kingdom came without observation and is within us, and as all who are in Christ are of every nation on this earth, then the kingdom of God is wherever the faithful are gathered.
See my post The Gathering of The Elect at ShreddingTheVeil as well as the Signs of The Feasts Parts I-III here, here, and here.