There are countries that grant citizenship based on the fact that one of your grandparents was a citizen. So, you could be born in the US to two citizen parents and still have "divided loyalties". Which is obviously absurd!
In 2011, the Congressional Research Service published an essay on the NBC question. It concludes:
In textual constitutional analysis, it is understood that terms used but not defined in the [Constitution] must, as explained by the Supreme Court, “be read in light of British common law” since the Constitution is “framed in the language of the English common law.”In addition to historical and textual analysis, numerous holdings and references in federal (and state) cases for more than a century have clearly indicated that those born in the United States and subject to its jurisdiction (i.e., not born to foreign diplomats or occupying military forces), even to alien parents, are citizens “at birth” or “by birth,” and are “natural born,” as opposed to “naturalized,” U.S. citizens. There is no provision in the Constitution and no controlling American case law to support a contention that the citizenship of one’s parents governs the eligibility of a native born U.S. citizen to be President.
Although the eligibility of native born U.S. citizens has been settled law for more than a century, there have been legitimate legal issues raised concerning those born outside of the country to U.S. citizens. From historical material and case law, it appears that the common understanding of the term “natural born” in England and in the American colonies in the 1700s may have included both the strict common law meaning as born in the territory (jus soli), as well as the statutory laws adopted in England since at least 1350, which included children born abroad to British fathers (jus sanguinis, the law of descent).
The weight of legal and historical authority indicates that the term “natural born” citizen would mean a person who is entitled to U.S. citizenship “by birth” or “at birth,” either by being born “in” the United States and under its jurisdiction, even those born to alien parents; by being born abroad to U.S. citizen-parents; or by being born in other situations meeting legal requirements for U.S. citizenship “at birth.” Such term, however, would not include a person who was not a U.S. citizen by birth or at birth, and who was thus born an “alien” required to go through the legal process of “naturalization” to become a U.S. citizen.
The “essay” is all well and good and reminiscent though not quite as in depth as frequent discussions here by we “birfer morons” in years past. The essay you found however is not actually conclusive and does not give relevant example cases thus is the opinion of one Obama supporting government employee. But I am extremely glad that you are now resorting to research and reason instead of insults this afternoon which I find very refreshing.