Jesus said, "My kingdom is not of this world. If it were, my servants would fight to prevent my arrest by the Jewish leaders. But now my kingdom is from another place." (John 18:36; TNIV)
"You are the salt of the earth. But if the salt loses its saltiness, how can it be made salty again? It is no longer good for anything, except to be thrown out and trampled underfoot.The kingdom of heaven/God was at the heart of the good news that Jesus brought in person (as king), word and deed. This kingdom had come near in him and came to reside in the midst of his disciples. It was a kingdom not of this world and its kingdoms. It was from another place.
"You are the light of the world. A city on a hill cannot be hidden. Neither do people light a lamp and put it under a bowl. Instead they put it on its stand, and it gives light to everyone in the house. In the same way, let your light shine before others, that they may see your good deeds and glorify your Father in heaven. (Matthew 5:13-16; TNIV)
Jesus' "Sermon on the Mount" (Matthew 5-7; see also Luke 6:17-49; 11:1-13) is a summons to and declaration of this kingdom. Jesus' followers are said to be the salt of the earth, the light of the world (a city on a hill). This kingdom then, though not of this world, is to impact this world. It is not something confined to Jesus' followers during that time, but is for all who belong to the community of Jesus today. This is no less than the new Israel in Jesus the Messiah. Blessed to be a blessing to all nations.
If these things are true, then why do we as Christians seem to be so strongly identified with the kingdoms of this world? Jesus is Lord. Caesar is not.