How many profess to having been born again, but do not understand that when one is born again they both know and have entered the Kingdom of God? So many professing to have been born again, don't believe the Kingdom of God has come. Why would one believe they have been born again yet deny the Kingdom of God has come?
You simply have confused what being 'born again' really is, and what Jesus said about the kingdom being 'within you' is about.
No one will properly understand that without first understanding the two different dimensions of existence written of in God's Word, the earthly one vs. the one of Spirit.
Where is God's Abode today? On this earth? No! Inside the earth? God forbid, no! In the sky atmosphere around the earth? No, because the sky is part this material creation, and Apostle John said in John 4 that "God is a Spirit". And in John 3:6 Jesus said, "That which is born of the flesh is flesh, and that which is born of the Spirit is spirit."
The "born again" phrase in John 3 actually means "born from above" in the Greek by accepting as our Savior Jesus Christ. It is about our spirit that dwells inside our flesh body being made a 'new creature' by The Spirit. It does not mean our flesh is turned into some new creature. That is the 'born again' idea Jesus was referring to in John 3 to Nicodemus.
Per Hebrews 4:12, God made us with 3 parts:
1) a spirit,
2) a soul, and
3) joints and marrow, put for a flesh body.
Matthew 10:28 and Ecclesiastes 12:5-7 reveal that our spirit & soul together is separated from our flesh body at death of our flesh, showing that our flesh is not the real 'us' (i.e., person). Our spirit with soul remain attached together, and return to The Father in that world of Spirit. But our flesh body goes back to the ground where it was taken from, and decays back to the earthly elements. Solomon revealed in Eccl.12 about a "silver cord" that keeps our spirit and flesh together while alive upon this earth. That cord is severed at flesh death.
If the Christian does not understand that as per the written Bible Scripture, then how will they understand what "born again" literally means, and what Jesus meant when He said "the kingdom of God is within you"?
Christ's Kingdom is manifest already, here on earth,
but in The Spirit ONLY, NOT physically yet. That is what He meant when He said the kingdom of God is within you.
His Church is of The Spirit, and those in Christ are foundation stones in the Temple of The Spirit. This is why Communists like Joseph Stalin could close Christian Churches in Soviet Russia all he wanted, but Christ's Real Church of The Spirit never ended there! The devil cannot destroy Christ's Church off this earth, as much as he would like to! That is because Christ's Church is of The Spirit, and not simply some building or lawn with a sign on it that says 'Church of...'.
On a deeper note -- when Christ's future Kingdom will be manifest on earth in the future, literally in the physical, it will still be manifest in The Spirit. How? you might say. It is because on the day of His future return, He is going to change us all to the "spiritual body". That world to come will not involve us in flesh bodies anymore, and that includes the resurrection of damnation also. The future resurrection is not about getting a new flesh body, nor our old flesh in the casket being raised to a new flesh body.
God is going to join this earthly dimension with the heavenly dimension, both together in the same space and time,
on earth. That is how He is going to return with His Garden of Eden back to this earth where it once was per Genesis 2, with His River of the waters of life feeding other rivers upon this earth, and the Tree of Life.
