I would say that the theme of the whole bible would be to become one with God. Isn't that the whole reason for everything? What you say is technically correct about all nations receiving the blessing of the Gospel. I just think the main problem is that all that means to most people is a set of rules to live by and argue over. The gospel should be that God has made a way for you to be one with him.
That is the story of the fall. We lived in the presence of GOD. (In your words we were one with GOD) We lost that. GOD immediately set in place our redemption at the fall.
Genesis 3:15
The law was pre Jesus, post Jesus grace. No need to argue about the laws.
The Abrahamic covenant was to bring that blessing to ALL the nations. As it was in the beginning.
