In fact, in 1787, no one over 11—not George Washington, not John Adams, not Thomas Jefferson—was a “natural born citizen” of something called "the United States of America.” The first “natural born citizen” to enter the White House, by my count, was Martin Van Buren in 1836—who was born in 1782, five years before Philadelphia.
I don’t think that the Framers were even thinking about potential presidents born to American parents abroad. Their concern was naturalized citizens, and it was a lot more immediate and urgent.
Under British law, a foreigner could acquire “naturalized citizenship” only one way: by special Act of Parliament. Prince George of Denmark was naturalized in 1689 to permit him to become to marry Queen Anne. Despite 17 pregnancies, Anne never gave birth to an heir. Toward the end of her reign, this lack led Parliament to pass the Sophia Naturalization Act of 1705, by which Sophia, the Electress of Hanover, was made a British subject, and “the issue of her body” became heirs to the British throne. Sophia’s son ascended to the throne in 1714 as George I. Had the Act not been passed, none of the Georges could have succeeded to the throne.
In other words, the Framers knew one thing about naturalization: It was the way countries shopped for kings.
In 1787, the United States seemed to be falling apart, and many worried that it might end up with an imported European monarch. In 1786, Nathaniel Gorham, later a Philadelphia delegate, had apparently written to Prince Henry of Prussia inquiring whether he’d enjoy being America’s head of state. Newspapers during the Convention speculated that the delegates were offering the Crown to Frederick, Bishop of Osnaburgh, younger brother of George III (and later Duke of York). That wasn’t true, but some worried that the danger of foreign princes might not abate even after ratification of a new Constitution. Someone might propose Henry or Frederick as the new president. The newly naturalized president might make his son vice president. Since many delegates expected presidents to be reelected every four years until they died in office, the result would be a de facto monarchy.
That fear probably inspired the “natural born citizen” clause. I can’t find any evidence that the Framers wanted to discriminate against the children of Americans anywhere. The first naturalization statute, passed in 1790, said that “children of citizens of the United States, that may be born beyond sea, or out of limits of the United States, shall be considered as citizens of the United States.” (Citizenship did not extend to such children if their fathers had never lived in the U.S.)
The endless parsing of the Framers’ unspoken thoughts on this subject—as on so many others—does our politics a disservice. There’s no coded message in the “natural born citizen” clause. The Framers set up a government and left a lot of things—including supervision of citizenship—to Congress. In passing the Immigration and Naturalization Act, Congress extended citizenship to children of Americans born abroad.