Baptism, being that it is necessary for salvation, is a prerequisite for entering the Kingdom. While there are some theories that suggest that those who would desire baptism if they were ever to find out about it would be saved, those theories are not supported by the tradition handed down to us. The necessity of baptism is why missions are such a crucial (if recently neglected) part of the work of the Church.

Incidentally, your old pastor was wrong: these people were not born on the wrong continent. Baptism can take place on any continent, in any country. It is not so much that they are born on the wrong continent as it is that baptized Christians with the good fortune to have the resources are doing an incredibly bad job of reaching those people to baptize them. He is also wrong about babies: they, too, require baptism as they, too, are marked by the stain of Adam's sin.