The Kingdom of God has several meaning according to different Scriptural passages.
In one sense, since God is the Creator of the whole universe, the Kingdom of God is His rule over all the whole universe.
In another sense, it is the rule over the hearts and minds of believers who submit to God’s authority. Those who defy are simply not of this Kingdom. And it can only be entered into by being born again.
Yet another, it can refer to the millennium rule of Christ when He returns.
Christ’s present hidden spiritual reign in our hearts and minds, the Kingdom of grace, will culminate in His future physical reign, the Kingdom of glory, when He returns.
The 7 mountain mandate popularized by the NAR is an unbiblical movement to re-define the Kingdom of God. It preaches that all Christians are required to create a worldwide kingdom for the glory of Christ through dominating education, religion, family, business, government & military, arts & entertainment, and media.
Our Lord did not come to overthrow the Roman empire. He made it clear that His kingdom was not of this world at that time but in the hearts and minds of those who would follow Him. He will rule the whole world when He returns.
In Luke 19:11-12, when Jesus was near Jerusalem and the people thought that the Kingdom of Israel would be restored, He answered with a parable that the nobleman would go away to a distant country to be appointed king first and then return. In Acts 1:3-8, He appeared over 40 days to the apostles and spoke about the kingdom of God. The apostles also asked the same question as to when the kingdom of Israel would be restored. He replied that only God the Father set the date and time by His own authority.
Meanwhile, He warned that we will be hated because the world hated Him first and we will have persecution and a great falling away instead. Luke 21; 2 Thess 2:1-3; John 15:18-21.