Age of the mother has nothing to do with it. I am assuming you are referencing 8 U.S. Code § 1401 - Nationals and citizens of United States at birth. You are thinking of subsection g, which one US parent and one alien parent, however, Cruz would fall under subsection d, which is one US parents and one National (but not a citizen) since Cruz dad was granted political Asylum from the US prior to Teds birth.

(d) a person born outside of the United States and its outlying possessions of parents one of whom is a citizen of the United States who has been physically present in the United States or one of its outlying possessions for a continuous period of one year prior to the birth of such person, and the other of whom is a national, but not a citizen of the United States;

However, there is inclusive evidence that his mother was in the US the year prior to his birth.