BO’s mother was born in Wichita, Kansas.
She was always a US citizen.
Also, I really doubt this law was intended to affect a parent who was themselves a natural born citizen who never lived outside the US - I think it was aimed at naturalized citizens who had a child with a non-citizen. I dont think that law applied to someone who was born in the United States. Heck if thats the case then millions of Americans who are 4th or 5th generation, born to mothers under 21, with immigrant fathers, arent natural born citizens.
If
The truth is: it’s complicated.
http://www.iht.com/articles/2004/06/02/expats_ed3_.php?page=1