The entire thing is nonsense. If one went out-of-country in that day, the trip would likely take months. It cannot have been infrequent that a child was born out of country - to include ship-born which would be under the flag of the ship. Of course it has always been so that the child assumes the native state of his parents.
Otherwise history would be replete with tales of mad dashes with pregnant women to get them to an American embassy or an American ship in order to preserve the child's natural rights. I can recall no such thing.