Mitt Romney was born in Michigan, not Mexico. Both of his parents were American citizens. His father, however, was born in Mexico of American parents. Barry Goldwater was born on American soil, albeit a territory, not yet a state. McCain was born on an American military base where his father was active duty military. Each of these men are American citizens at birth, born of two citizen parents. McCain and Goldwater, as determined by congress, did meet the requirement of essentially being born on American soil.
It was George Romney who was born in Mexico.
The law DOES NOT require two citizen parents:
A child born abroad to one U.S. citizen parent and one alien parent acquires U.S. citizenship at birth under Section 301(g) of the INA provided the U.S. citizen parent was physically present in the United States or one of its outlying possessions for the time period required by the law applicable at the time of the child’s birth. (For birth on or after November 14, 1986, a period of five years physical presence, two after the age of fourteen, is required. For birth between December 24, 1952 and November 13, 1986, a period of ten years, five after the age of fourteen, is required for physical presence in the United States or one of its outlying possessions to transmit U.S. citizenship to the child.) The U.S. citizen parent must be the genetic or the gestational parent and the legal parent of the child under local law at the time and place of the child’s birth to transmit U.S. citizenship.