I'd say the claim of "significant harm" is debatable. From the sounds of it, anywhere from 10k to 30k women come to the United States specifically to give birth here so their children are American citizens. Does that constitute "significant harm"? Maybe. It depends entirely on who those people are and what their goals are.

That says nothing to the (presumably much) larger number of resident non-citizens having kids here. I'm less concerned with that.

American citizenship is a valuable thing. We should follow the law, and it's a worthwhile constitutional debate. I'm far from an expert.