Presently, the kingdom of God is in heaven (2 Timothy 4:18, Hebrews 12:22-24), and is on the earth spiritually within Christians (Romans 14:17, Luke 17:21). In the future, the kingdom will come fully upon the earth as it is in heaven (Matthew 6:10). It will be physically (Luke 22:30, Matthew 19:28) on the earth (Revelation 5:10), first during the future millennium (Revelation 20:4-6, Revelation 2:26-29, Psalms 66:3-4, Psalms 72:8-11, Zechariah 14:3-21) and then on the new earth (Revelation 21:1-8).
Jesus' kingdom is Israel (John 1:49, John 12:13-15, John 19:19, Luke 22:30). That's why at his 2nd coming, he will sit on the earthly throne of David (Luke 1:32-33, Isaiah 9:7) and restore the kingdom to Israel (Acts 1:6-7, Acts 3:20-21). Jesus is, in his humanity, the son of David (Matthew 1:1, Matthew 21:15-16, Romans 1:3), of the house of David (Luke 1:69). So at Jesus' 2nd coming, he will restore the tabernacle, the house, of David (Isaiah 16:5, Amos 9:11), to its royal glory (2 Samuel 5:12), which it had lost (2 Kings 17:21a). And Jesus will fulfill the prophecy and prayer of 2 Samuel 7:16-29. And he will bring salvation to all the unbelieving elect Jews of the house of David. For they (along with all other unbelieving elect Jews) will come into faith in him when they see him at his 2nd coming (Zechariah 12:10-14, Zechariah 13:1,6, Romans 11:26-31). And so they will all become part of the church at that time, for there are now no believers outside of the church (Ephesians 4:4-6).