The summary: The child of an unwed American mother cannot be granted automatic citizenship more quickly than the child of an unwed American father.
http://www.npr.org/2017/06/13/532674073/high-court-strikes-down-law-favoring-unwed-mothers-over-unwed-fathers
http://www.npr.org/2017/06/13/532674073/high-court-strikes-down-law-favoring-unwed-mothers-over-unwed-fathers