Is the child of a Mexican mother a Mexican citizen?
I would not be surprised if it was a dual citizenship scenario.
I don’t know. That’s a question of Mexican law. Which means it’s irrelevant to the question of whether that child, if born here, is a U.S. citizen - last I checked, whether a person is a U.S. citizen is not dependent on foreign law.
To illustrate, here’s another hypothetical. Suppose Mexican law stated that if a child has at least one grandparent who is a Mexican citizen, then the child is born a Mexican citizen as well. Would that mean that anyone with a Mexican grandparent would NOT be a U.S. citizen? Of course not, because Mexican law has no bearing on U.S. citizenship.