Matthew 28:19-20 Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.
God has commanded us to preach the Gospel to every creature but He has also told us to disciple nations. There are three things that I would like to point out that we can conclude from the command to teach all nations.
First, Christianity transcends nations. While countries come and go the church remains. One hymn puts it this way:
Crowns and thrones may perish, kingdoms rise and wane,
But the Church of Jesus constant will remian,
Gates of hell can never 'gainst that Church prevail;
We have Christ's own promise, and that cannot fail.
Second, God sees people as being parts nations. Many in the world want to minimize national patriotism and instead replace it with alliegence to the earth. There are also some in the Church who do not want to think much of their national citizenship. While we are subjects of Christ's Kingdom, we still ought to love and be loyal to our own nation just as we should love our earthly family even though we are part of God's family which is far more important. God is the one who established governments and divided mankind into nations at the tower of Babel.
Third, the preching of the gospel should have an effect on a nation as a whole. All the people in any earthly nation will probably never be saved but the commands of Christ and God's power will affect an entire nation when the great commission is carried out. The Bible will change the culture of any people who are taught it. The government of a nation will also be affected. A nation cannot follow both God's law and Sharia law.
While nations are to be taught according to the great commission, we who are Christians are the one's who must do the teaching out of obedience to God.