"33But seek ye first the kingdom of God, and his righteousness; and all these things shall be added unto you." (Matthew 6: 33)
Jesus exhorted the Israelites of His day not to take confidence in their ethnic status as Jews, nor seek to overthrow the Roman Empire, but seek to entry into God's eternal kingdom.
This Kingdom comes to us through His Holy Spirit, which has been poured out to us now that Jesus Christ has died on the Cross and now sits at the right hand of God the Father ministering on our behalf (Romans 8: 31-32):
"For the kingdom of God is not meat and drink; but righteousness, and peace, and joy in the Holy Ghost." (Romans 14: 17)
As further proof that the Kingdom comes to us because of all that Christ Jesus did, consider this wonderful declaration:
"Who hath delivered us from the power of darkness, and hath translated us into the kingdom of his dear Son:" (Colossians 1: 13)
Where were we before we believe on Jesus? Paul relates the following to the Colossians:
"And you, that were sometime alienated and enemies in your mind by wicked works, yet now hath he reconciled" (Colossians 1: 21)
and also to the Ephesians:
"That at that time ye were without Christ, being aliens from the commonwealth of Israel, and strangers from the covenants of promise, having no hope, and without God in the world:" (Ephesians 2: 12)
Here, Paul explicitly refers to state, kingdom like citizenship.
Because of Jesus Christ, we are blessed as adopted children of God the Father:
"13But now in Christ Jesus ye who sometimes were far off are made nigh by the blood of Christ. 14For he is our peace, who hath made both one, and hath broken down the middle wall of partition between uslit. citizenship] is in heaven; from whence also we look for the Saviour, the Lord Jesus Christ:" (Philippians 3: 20)
and
"And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together." (Romans 8: 17)
and
"That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel:" (Ephesians 3:6)
Because we have received a new citizenship in the Kingdom of Heaven through Christ, we are no longer strangers, alienated from God the Father's blessed, eternal Kingdom which He gives in His good pleasure to those who believe (Luke 12: 32)