Is that not the goal of the whole plan? The cruelty is the point.
It won't impact their right to vote, which wouldn't be for a few more years anyway.
But then again, I have no idea what problem the US opponents of birthright citizenship are trying to solve.
As for the underlying issue, I'm not sure, but I suspect it might be related to the so-called "$5M gold card." Perhaps the goal is to make citizenship more exclusive and drive up its perceived value?
French nationality law (in French, obviously): https://www.immigration.interieur.gouv.fr/Integration-et-Acc...