I would like to remind everyone that this was a philosophy and law that began in 1790 and was repealed in 1965. Undoubtedly, since the S.o.S. began in 1692-93, almost a century before hand, and that MACUSA began (likely under a different name, like "Magical Congress of North America" or some such, since the U.S. didn't exist in that time) the same year the S.o.S. was established, MACUSA likely had laws dealing with these situations.

The most likely and reasonable would be introduction of the parents to the magical community on a temporary basis to test if they could be trusted to keep it secret, with obliviation of the knowledge of magic and their child should they prove they cannot. Rappaport's law, however, forced them into an "act now, (reversible memory charm) can we trust them (observe and report) later" approach, regrettably. In all likelihood, all reports during this time came back as "Parents untrustworthy with the Secret of Wizardkind."

Since the repeal of Rappaport's law, however, after two centuries nearly of total isolation from their no-maj counterparts, it is entirely likely the Rappaport's Law era law's concerning no-maj parent's continued and took some HEAVY and staunch activism to have those law's repealed over time. I see the law's and social outlook in the area of No-maj parents from 1965 to the 1990's and on to today in the same as that era's improvements concerning inter-racial marriage among no-maj's during this time. Disconcerting by today's standards by far, but always ever improving and progressing.

It is my belief, if I may give it, that the relationship of no-maj born's, and their parents specifically, with the magical communities in America is actually a euphemism  for the outlook on inter-racial marriages by American society.

However, all of this is conjecture. It is still unknown, by J. K. Rowling's Canon, if there even is a way for Ilvermorny or MACUSA to know when a Magical child is born! The quill and book Hogwarts uses could, POSSIBLY, be used, but that would mean only one institution in the whole world would have direct access to the knowledge base that is the future of the wizarding world. This is an unlikely scenario as it states that this is the only method for a student to be accepted into HOGWARTS. It is also said that this book and quill had not been touched by human hand since the founders, and, from what I can see a lot of the known magic during that time has since been lost.

To sum it up, the answer is... Rowling has yet to answer this specific question, and until she does (which is seeming less likely as the years pass that she will) it is best for you to find you're own answer, as much as that may suck.

Sorry, I'm both a Hufflepuff and a Ravenclaw, and would likely be sorted into Horned Serpent at Ilvermorny.

HOLY CRAP, I didn't realize I wrote a book!!!