The earth is Satan’s kingdom. We are behind enemy lines, so to speak.
I presume you refer to 2 Cor 4:4, and or John 12:31; 14:30. It is a horrible misuse of scripture to use those to teach against the kingdom of God on earth. It does much damage to the prophets, the parables, the psalms, and the gospel of the kingdom. I understand why you would repeat it. It is widely taught as such. But this is a part of the reason America is in the moral dilema we are in. That teaching makes Christians irrelevant in todays world. In fact, it makes them somewhat useless to God's kingdom.
Matthew 28:18 And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth.
Romans 4:13 For the promise, that he should be the heir of the world, was not to Abraham, or to his seed, through the law, but through the righteousness of faith.
Psalm 24:1 The earth is the Lord's, and the fulness thereof; the world, and they that dwell therein.
Psalm 115:16 The heaven, even the heavens, are the Lord's: but the earth hath he given to the children of men.
If you read the parable of the tares carefully, you will see that the tares are in the field which is the world. Later you see the tares are gather out of the kingdom where they have been growing. They were growing in the field, which is the world. The kingdom is the world.
Revelation 11:15 And the seventh angel sounded; and there were great voices in heaven, saying, The kingdoms of this world are become the kingdoms of our Lord, and of his Christ; and he shall reign for ever and ever.