There is nothing whatsoever in the debate that explicitly states, implies, or contextually suggests that the framers of the 14th Amendment meant to grant birthright citizenship to the children of illegal immigrants. They don’t talk about illegal immigration much because on that question, there was no need for debate. The children of persons “subject to any foreign power,” “owing allegiance to anybody else” were—all agreed and the law already declared—not citizens.
When they do talk about immigration—particularly Senator Cowan—they express concern that the amendment be carefully drafted so as not to allow or provoke unchecked immigration by offering too broad a definition of citizenship. (As an aside, I note that Senator Cowen’s long speech is quite triggering to our ears in 2018. It’s amusing to be called “racist” by people whose arguments rest on the views of men whose words I blush to read.)
To return to an earlier point, my encouragement at seeing a liberal defend originalism was clearly misplaced. First, because he did so incompetently. Second, because he did so insincerely. Indeed, his incompetence was in service to his insincerity. The goal, as ever for liberal jurisprudence, is to arrive at the desired policy result. If an originalist interpretation can get the liberal there, he will use it. If he can conjure a false originalist interpretation, he will use that—especially in a debate with an actual originalist. If no appeal to originalism, true or false, is possible, he will appeal to precedent and call it binding for all time. And if the appeal to precedent turns out to be impossible, he will invoke the “living Constitution.”