The only sovereignty in the Kingdom of God will be that of God as exercised by His son, the Lord Jesus Christ, and the saints. See Daniel 2:44; 7:22,27; Revelation 5:9,10.
However, nations will still be identifiable during the Millennium - see Zechariah 14:16-19 as an example.
Here are links to useful information on this topic:
I hope you have found this helpful.
God bless,
Mike