They already collect blood samples in the states to test for incredibly rare congenital defects. When we tried to decline testing, we were threatened with a CPS case and the removal of our just-born child. I imagine leaving the hospital at that point would have gone very poorly for us from a legal point of view.
Supposedly the samples are destroyed "eventually," but we got several conflicting answers as to when that was. No one had any expertise in anything even privacy-adjacent, so what we were giving "consent" to was never clarified.
From our experience, I think a law that maintained DNA samples for all births in the US would easily sail through despite a very small and impotent opposition. I hope I am wrong.