And Jesus came and spoke to them, saying, "All authority has been given to Me in heaven and on earth. Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all things that I have commanded you..." (Matt 28:19,20)
Almost every time I have heard The Great Commission uttered, preached, or explained, people seem to understand it as taking the Gospel to every individual person in every country. It is as if they translate it as saying, "Go and evangelize every person everywhere." I have come to believe that it means so much more than that.
Without getting into a lexical debate, check this out for kicks. One Greek lexicon defines the Greek word, "ethnos," (nation) as, "The largest unit into which the people of the world are divided on the basis of their constituting a socio-political community." In the New Testament, "ethnos" is also used to denote "Gentiles" or non-Israelites, but in many texts it also has clear political / nation-state connotations (Mt 24:7, Mt 24:14, Mk 11:17, Jn 18:35, Acts 24:17). I suppose you could argue that the word in the context of Matt 28 could just as easily be rendered, "heathen," or "Gentiles," but I think you would be ignoring the rest of Scripture.
The good news of the Gospel is that God is restoring the whole world, not just individual souls residing in each country on earth. The Gospel extends to every part of life and every system - even political ones. Jesus isn't called the "Lord of lords" and "King of kings" for nothing. God's promise to Abraham wasn't just that he would be the father of the Jews. God's promise was that Abraham would "be a father of many nations." (Gen 17:4-6) In Romans 4:13, Paul interprets this as meaning that Abraham would "be the heir of the world."
It is unsettling for many Evangelicals in America to realize that the United States is not a Christian nation. Our systems may have the residue of "Judeo-Christian" ethics, but our nation itself has not been discipled. Individual souls may have been converted, but our systems are fundamentally secular and separated from the Gospel and the word of God. I don't know what to expect in the case of the United States, but I do believe that in time the church will succeed in discipling all nations. (Acts 3:19-21)