"The child of an alien, if born in the country, is as much a citizen as the natural born child of a citizen, and by operation of the same principle. "
The phrase, "as much a citizen" means that the person in question is "as much" a natural born citizen as a person who had two U.S. citizen parents.
"As much as" means "Equal To" and equal to means the very same.
Moreover, the Justices did not say "if born in the country, is as much a citizen as the natural born child of two citizens....."
Instead, they said "if born in the country, is as much a citizen as the natural born child of a citizen..."
Obama has one parent who was a citizen.
I disagree. I don’t think your reading of the phrase to is correct and there is no evidence that the Supreme Court has ever adopted such a position or for that matter any other court. If the Supreme Court had wanted to say that such a person is a “natural born citizen” it would have said so; instead it said that such a person is as much a “citizen” as a natural born person is. It thus deliberately contrasted the two different phrases. Your interpretation is strained.