Granted, the church is not a nation like the United States or Russia is a nation.  The church is not a physical country.

The church is a kingdom, though.  Members of the church are told that God transferred them into Christ’s kingdom (Col. 1:13).  Members of the church are told that they have received a kingdom which cannot be shaken (Heb. 12:28).  Thus, in that sense the church is like a nation.

Again, this kingdom which is the church is not a physical kingdom.  Jesus told Pilate that His kingdom was not a worldly kingdom (John 18:36).

Yet, make no mistake, Christians.  We serve a King, the King of kings.  God Himself called us into this kingdom by the gospel (1 Thess. 2:12; 2 Thess. 2:14), the gospel in which we stand (1 Cor. 15:1-2).  We are citizens of a heavenly kingdom/nation.  We are members of Christ’s church.  Let us never forget that, and conduct ourselves accordingly.