In short, my views go like this (I am essentially modifying Augustine’s discussion in Bk 19 of City of God).
*Since I am an ontological realist, I believe that the nations in the mind of God (prior to their being revealed in Genesis 10/Acts 17) are real entities. They are not simply “names” or “linguistic constructions.” TO argue such is nominalism, and therefore wrong.
These entities (call them countries, nations, nation-states, I don’t care. The literature on this is more or less terrible) *MUST* be united by an agreement to share the common objects of love. Full stop. This.Is.Augustine.
However, while these are real entities in the mind of God, they are not absolute. They are contingent upon the vicissitudes of history (since history is in time and time is in flux, this is not surprising). So if some nations cease or others marry/breed in our out of these nations, that’s life.