If as stated above (I have no idea of the facts personally) George Romney’s father rencounced his US citizendhip when he fled to Mexico, and then George was therefore born in MX to a father who was not a US citizen, his status seems quite dubious.
George Romney's father Gaskell was born in Utah in 1871, lived in Colonia Dublán from around 1890 until about 1910, and died in Salt Lake City in 1955. He was not a polygamist. His wife Anna died in 1926 in Salt Lake City and he married her younger sister Amy in 1927 in Salt Lake City.
