When Jesus said that, He had been rejected by Israel as their King-Messiah, therefore the Kingdom of God was visible only to God.
But you have been presented with Scriptures pertaining to His second coming, when His Kingdom will be a real, literal, visible, and tangible Kingdom on earth. And you continue to persist in your erroneous understanding of the difference between the first and second comings of Christ.
Of course it is hard to be rid of false indoctrination, but since you have a Bible, you have no excuse.