It doesn't matter where Obama was born.
He only has one US citizen parent, and there's some question whether Anna Dunham could convey citizenship because of her age.
Also, and I didn't focus on this part of your post before:
If he was natural born he will always have US citizenship.
You are conflating two issues -- you can be a citizen and not be a "natural born" citizen. Check out this chart:
Natural Born Citizen -- The Law