As Jesus continues to teach about the Kingdom of God, which begins with the spiritual segment, he introduced and here teaches that it ends with its governance of the entire earth. The earth will be governed through an absolute monarchy with Jesus reigning supreme as the king over the world with its headquarters in Jerusalem. This is clear from the Psalms and the prophets. Even though the throne will be in Jerusalem (aka Zion) the dominion of Messiah‚Äôs rule will be the entire earth.
6Yet I have set my king Upon my holy hill of Zion. 7I will tell of the decree: Jehovah said unto me, Thou art my son; This day have I begotten thee. 8Ask of me, and I will give thee the nations for thine inheritance, And the uttermost parts of the earth for thy possession (ASV 1901).
One well-known passage from Isaiah that seems to get more emphasis at Christmas due to its introduction of the virgin birth actually has much more to say regarding the future earthly Messianic Kingdom.