Since you're US-based, I'd like to run this thought past you: I don't know if you're into Harry Potter much but I keep thinking about the canon fact that supposedly the USA only has, implication is ever had, ONE wizarding school in the vein of Hogwarts (Ilvermorny, for reference - East Coast, North); do you find this to seem a little implausible, given if nothing else the historical regional splits and cultural differences in our country? Because I'm wondering how to reconcile that in fic. :\
Oh man, I have a solid hour-long rant about how implausible Ilvermorny is. There is just so much suspension of disbelief (plus an utter lack of historical knowledge) that JK Rowling was depending on for that school, and none of it worked for me.
First of all, you’re 100% on track with the issues around regional splits and cultural differences. The US is huge. Like, it’s [number 3 on the list of largest countries by land mass], which JK Rowling definitely did not take into consideration, from both a technical and cultural standpoint. Going off of the knowledge we have from HP canon, there are limited ways for families to travel: most don’t seem to want to apparate with their children, floo powder and portkeys are logistical nightmares for the Ministry, and brooms are expensive and not feasible for long distances. But a train to Ilvermorny could take days, if not a good week depending on where you’re from (I’m not even going to touch Alaska and Hawai’i here). Also, the Appalachians are relatively easy mountains to climb for even semi-experienced hikers. If you want a school up in the mountains out of the reach of Muggles, put it in the Rockies or up on Denali.
From a cultural perspective… America is split into very distinct cultural regions, and each of those regions has smaller, less distinct parts dividing them. I will say that sending all magical children to the same school would be great for diversity (so many different people in one place! Sharing knowledge and experiences! Learning about people from outside their limited scope! It’s the breeding ground for tolerance and peace!), and that, given English wizards history with being willing to send all their kids to one school, it’s likely they would be willing to, they just may not be physically able to.
But, this brings another issue up… America is not just English descendants. For one, we have to take the Native tribes into consideration. Now, Rowling’s claim is that Native wizards did not hide. I have two points of contention to this: 1) You cannot claim anything universally with Native peoples. At the moment, there are over 500 federally recognized tribes, but before the English colonialists arrived, there were so, so much more. That’s 500+ societies, each with their own beliefs, practices, and customs. Assuming wizards are real, I highly doubt each and every one of the tribes would be pro-wizard.
2) If even half of the Native tribes had active, known wizards in their ranks, the English settlement of America would have gone much, much differently. Remember, wizards in England were in hiding, and have a history of absolutely no involvement with muggle affairs. So that brings two questions - a) what incentives would many wizards have to come over here? and b) why would the ones that did help the English settle the place, and not just go out and try to set up their own society or join a pro-magic tribe? So, we’d have to assume that there are no wizard fighting on the side of the English, but there are wizards fighting on the side of the Natives. I’m not seeing many situations where the Native tribes don’t stop the colonization, unless Native wizards are as susceptible to European diseases as their non-magical brethren. That would change the history of America, and the rest of the world, profoundly.
tl;dr: JK Rowling’s version of events is honestly implausible in every conceivable way. For it to work, there would need to be fundamental changes to the situation. One, either more than one magic school, or an easy, non-dangerous, and inexpensive method of moving hundreds (maybe thousands) of people from across the country to Ilvermorny. If you go with more than one magic school, you could easily put one in each region of the US - Wikipedia has a pretty cool breakdown of the different regions and the districts within each you can base school placement on. (Though I’d personally put Alaska and Hawai’i in their own regions.)
And two, a different assumption of Native tribal relations with magical folk. That can go a lot of ways: Most tribes aren’t pro-magic; there’s too much in-fighting between wizards of different tribes to focus on the English threat; the proportion of wizard-to-muggle is even lower among Native populations than European; English wizards did get involved in colonization for some reason… there are probably more I’m not thinking of. The issue with a lot of these is that you’d have to know a fair amount about different Native tribes’ sociocultural history to pull it off, which is out of the scope of my capabilities.