I’d like to see a reference to US law in 1961 that the child of a US citizen and a foreign citizen is not born a US citizen. I suspect this is inaccurate.
Ask and you shall receive. 8 USC 1401 Nationals and citizens of United States at birth. Be sure to see the notes section (link on the right in the box), the notes section says the eligibility for passing on US citizenship by the US Citizen parent was changed in 1986 from 10 total years of residency in the US, with 5 of those being after the person's 14th birthday, to 5 and 2 years respectively, as it currently is. .
The following shall be nationals and citizens of the United States at birth:
(a) a person born in the United States, and subject to the jurisdiction thereof;
...
(g) a person born outside the geographical limits of the United States and its outlying possessions of parents one of whom is an alien, and the other a citizen of the United States who, prior to the birth of such person, was physically present in the United States or its outlying possessions for a period or periods totaling not less than five years, at least two of which were after attaining the age of fourteen years
And from the notes:
1986—Subsec. (g). Pub. L. 99–653 substituted “five years, at least two” for “ten years, at least five”.
Stanly Ann was only 18 on Aug. 4, 1961, and for few months after that as well. She needed to be 19, under subsection g) listed above as it existed in '61.
The law also provides, redundantly restating part of the 14th amendment, that persons born in the US and subject to it's jurisdiction are citizens at birth. But remember though that the law only deals with citizenship, not natural born citizenship, the definition of which Congress has no power to change, under their power to define a uniform rule of naturalization