The Kingdom of God has always existed for eternity. Through Jesus, God created the earth and all physicality in 6 days, establishing His Kingdom on earth as it is in heaven.
When Adam sinned against God, the enemy’s kingdom invaded the earth. From Adam’s sin until now, the world has experienced a clash between the Kingdom of God and the kingdom of the enemy.
The re-establishment of the Kingdom of God back on the earth will be once again be fully realized on the Day when Christ returns in glory to establish His complete and total reign over everything, just as it was in the beginning, except this time, the serpent will NEVER be able to tempt any child of God ever again.
Col 1:16, Heb 1:8, Heb 1:10, Luke 17:20-21 NLT, Rev 11:15