So, you are saying that Obama was not a dual citizen at birth, and in effect, that a person born in the US cannot, today, be a dual citizen at birth.
The US does not recognize the demands made by a foreign country upon its citizens. If the person chooses to live as a US citizen, then no other country can force their citizenship upon him.
My sister was born in Germany of US parents. If Germany tried to enforce a claim of citizenship upon her, the US would tell them to take a hike.