Not to mention, WHY is it that magic is so bad a healing? Harry has bent gravity, manipulates elemental forces, breaks into minds and souls etc. He can even cross space-time and travel across the world like walking through a door (followed by some confusing and sometimes semi-dangerous terrain). But knitting skin and bone together is hard? Repairing ligaments is hard? I get that JB needs Murphy to be injured for the story. But the reasons stated for healing being tricky have NEVER been very convincing. I am not sure why either. It isn't hard to work into a relatively hard magic premise. The things modern science can do now is already incredible. I would expect wizards to at least be that good, if not better. But Harry won't look anyway.

The things modern science can do now are incredible - but the methods of getting there left a lot of dead patients along the way. And modern medicine still has a huge mortality rate despite all of our advances. In a system where the governing force of magic is famously unforgiving of things like mistakes and accidents, I can understand how medical magic would advance at a snail's pace. If you're using magic to heal a patient and mess up, you've just violated the First Law. Muggle medicine has thousands of doctors and researchers to advance their practices - wizards have a handful of people that all risk the death penalty if their experiment in cell regeneration goes wrong.

I feel like Maggie's citizenry is moot point anyway, since the only way Forthill could have gotten any kind of paperwork for her in a timely manner would have been to just forge the hell out of it. International adoption laws and citizenry laws are just way too complicated for it to take anything less than months to get Maggie greenlit in even the best of circumstances.  Plus, assuming Susan's name is even on the birth certificate (assuming there is a birth certificate - we literally have no idea under what circumstances Maggie was born), her goal in putting Maggie with a family was to hide her - and a paper trail with her name on it would have completely defeated the purpose. The smartest choice Susan could make in that situation would have been to forge a birth certificate with the adoptive parents' names on it.
And to further complicate things (please correct me if I'm wrong, it's been a while since I've read Changes), but wasn't Maggie's adoptive family violently murdered? And then the child missing from the murder scene shows up in the US a few days later with no records of crossing borders?

Forget social workers, all someone would have to do is shine a light on how Maggie even got to the US in the first place, and Harry would be under immediate investigation from the FBI, CIA, and any other agency that investigates international crimes - for murder, kidnapping, and human trafficking at the least.