Mudblood

Harry Potter

The Plot... Simplified...

 

Alright. We are 100 years in advance of the epilogue, which took place in 2017. (19 years after the final battle, which was June 98.) This puts us at 2117. So we can basically give the Muggles knowledge of magic, and, of course, dislike of it. And maybe stuff to counter it.
Currently, as we start, the Wizarding and Muggle worlds would be in a state of cold war. This means that while Muggleborns are not frowned upon, exactly, since it's someone else with knowledge of the potential enemy...well. I'd assume probably some get on the side of the wizards, and some might turn back to the Muggle side. Half-bloods might not be in danger, but are probably looked on a little unfavourably by more conservative purebloods.
At some point, it's likely the Cold War will stop being Cold and start being...War. There are likely already battles and such being fought in some places now (so the odd teacher could already have been involved in a skirmish or two, and most probably have, in fact) but mostly smaller ones. Things will heat up at some point...
Which...leaves everyone with fun.
The teachers need to decide what to do with Muggleborns, i.e. children of the potential enemy, who could also be swayed to their side. The kids need to pick sides, particularly the non-Purebloods. (I recommend any major villains be Muggleborn or Half-blood wizards, because they could easily dislike anyone involved in the magical world during such a time.)
Ultimately, since this IS the HP universe, the war will come down to Hogwarts, and the teachers and students here.
The reason why we are accepting all nationalities...isn't that simple? Outside of England, it's not a COLD War, is it? Some other places could have already had their magical schools compromised...