(ETA 12.25.12 at the end of the answer)
I think there probably were witches and wizards throughout the world, aside from Europe.
I looked through Fantastic Beasts and Where to Find Them, thinking that magical creatures must have very long histories in their countries of origin -- for example, as we know from Chamber of Secrets, a basilisk can live for 900+ years. I don't think it's a stretch to extrapolate that where there be dragons, there be witches and wizards! Therefore, I think each creature's country or continent of origin is indicative of the presence of generational magic folk.
Newt Scamander writes:
I have visited lairs, burrows, and nests across five continents, observed the curious habits of magical beasts in a hundred countries, witnessed their powers, gained their trust and, on occasion, beaten them off with my travelling kettle.
I was then but a lowly Ministry of Magic employee and leapt at the chance both to augment my pitiful salary of two Sickles a week and to spend my holidays travelling the globe in
search of new magical species.
Fantastic Beasts and Where to Find Them - Introduction
The International Confederation of Wizards argued the matter out at their famous summit meeting of 1692. No fewer than seven weeks of sometimes acrimonious discussion between
wizards of all nationalities were devoted to the troublesome question of magical creatures.
Fantastic Beasts and Where to Find Them - A Brief History of Muggle Awareness of Fantastic Beasts
Here's a quick paragraph about some of the magical creatures and their native countries:
The Acromantula is native to Borneo, so there's one country represented. Billywigs are native to Australia, and generations of Australian witches and wizards have attempted to lure Billywigs into stinging. Centaurs are thought to have originated in Greece. The Clabbert originated in the southern part of the United States and the Demiguise is found in the Far East. The Diricawl comes from Mauritius. The Antipodean Opaleye dragon is native to New Zealand; the Chinese Fireball dragon is native to China, where its eggs are prized in Chinese wizardry.the International Confederation of Wizards sent in exterminators to Peru in the late nineteenth century to eradicate an over-population of the Peruvian Vipertooth dragon. The Dugbog is found in North and South America; the Erumpent and Fwooper come from Africa. The Fire Crab is native to Fiji. The Kappa is a Japanese beast. The Lethifold¹ is found only in tropical climates. The Occamy lives in the Far East and India. The Phoenix comes from Egypt, China, and India. The Pogrebin comes from Russia.
ETA 12.25.12: I came across this bit regarding ancient Egyptian wizards in Prisoner of Azkaban. It's an excerpt of a letter from Hermione to Harry talking about the Weasleys':
Did you see that picture of Ron and his family a week ago? I bet he’s learning loads, I’m really jealous – the ancient Egyptian wizards were fascinating.
Prisoner of Azkaban - page 14 - Bloomsbury - chapter 1, Owl Post
Also, while European, Hermione mentions she's learned a lot about French wizards on her holiday in France and has adjusted her History of Magic essay with the new information she's uncovered. Two extra rolls of parchment's worth even.
¹ The Lethifold is not super common in highly-populated areas, but it does come into contact with humans here and there. Whether that means travelers from other regions is unclear.