I'd like to comment on your quote, " The earth is but one country and mankind its citizens. "
In a spiritual sense the Christian congregation is likened to one country, one nation at 1 Peter 2:9,5
So, to me God's congregation is but 'one spiritual nation', one spiritual country with its citizens, its subjects.
In other words, a nation of people not located on any map and has No borders, No boundaries found on any map.
Daniel chapter 11 is prophetic about that glorious beautiful spiritual land of decoration.
When God's enemies enter that spiritual land/nation it will prove to be their doom.
But Not the doom of righteous mankind as citizens, as subjects - Psalms 72:8, 12-14