Most Christians think that death leads to one of two places: Heaven or Hell. They also believe that the only way to enter Heaven is to is to have faith in the divinity of Jesus of Nazareth*. When people point out that this system is monstrously unfair, since many people are not exposed to the idea of Jesus, believers shrug their shoulders and say something about god being mysterious.
Oddly, confronted with an almost identical situation, many Christians reverse their position. When a child dies without having an opportunity to believe in Jesus, Christians invent the idea of an "Age of Accountability". If you don't reach the Age of Accountability before you die, then you're saved regardless of the state of your belief. There is literally no support in the Bible for this theory.
So what's the difference between damning people in distant countries and children that are only a few years old? The answer is obvious: People don't mind damning foreigners, but it makes them feel bad to think that their kids might go to Hell.
I personally like the Jehovah's Witnesses' take on the whole thing: they believe that everyone is simply dead and "asleep" until the coming of the "Kingdom of God". This has two plusses: it doesn't make god look like a complete jerk, and it's more supported by the bible than most interpretations.
*Both of these things are not very well supported by the actual bible. It's remarkable how many things in modern belief are based on incredibly vague or obtuse passages. Particularly the entire idea of The Antichrist being a person.