From Harry Potter and the Goblet of Fire, we’ve gleaned that there are three major wizarding schools that compete in the Triwizard Tournament. Hogwarts is located in England, Beauxbatons is in France, and Durmstrang is located in some snowy, mountainous region of northern Europe. But what about those magically blessed among us who happen to live on the continent of Asia? Or Africa? Or North America? The tournament would have been a perfect time to introduce some non-European schools. To her credit, Rowling does hint that there may be other foreign schools. But this still leaves us wondering how connected each wizarding continent is to each other. Does Lord Voldemort, for instance, provoke as much fear in Saudi Arabia as he does in Diagon Alley?
There is an historical background in this. The three schools in the Triwizard Tournament are three ancient schools from the ages in which trips were expensive and difficult (and dangerous). It is the same reason for which the Five Nations rugby tournament (Now Six nations) has only european nations in it: it is ancient.
If Five Nations were to be founded today, surely it would count with South Africa, Argentina, New Zealand and Australia. Wait, that actually exists: it is the World Cup.
It is the same with the Triwizard Tournament. Most probably if you were to select today's three best wizardring schools around the world, you may end up with some non-european one. But the tournament is not being created today.
It's the triwizard tournamement, as in "tri", three. There are only three schools that compete in it, it is something Beauxbatons, Durmstrang and Hogwarts team up for. Logistics-wise, these kinds of bonds tend to form with communities that are in proximity to one another.
An out of universe answer would be because of the scope of the book. Why do we need to learn more about Saudi Arabia or America in a book that is about a wizarding school in England? There's no real extra value from it.