Exactly, but you got the other part somewhat garbled. The law required the US Citizen parent to have resided in the US for ten years, five of which had to be after their 14th birthday. Thus she would have needed to be 19. But that only applies to births outside the US. So if he was born outside the US, he wasn't even a citizen, and unless naturalized later, would still not be one.
But his father definitely owned allegiance to a foreign sovereign at the time. That was Queen Elizabeth II of Great Britain, Kenya being a British Crown Colony at the time. By the time of the divorce of Stanley Ann and BHO Sr, it was an independent nation, but of course still a foreign sovereignty.
Obama would have also relinguished U.S. citizenship if adopted into Indonesia by his stepfather (Soetoro).