Does reproductive isolation apply to humans?

it is not possible.

reproductive isolation are mechanisms and processes that prevent two species to form a fertile offspring. In humans this is impossible, a population may be isolated e.g. someone in American and successfully reproduce a fertile child with someone in Africa or Asia. This is made possible by the same number of chromosomes. Also, mechanisms such as species recognition/pre-mating, post-zygotic (i.e. frailer to produce a zygote or a zygote is produced but it does not live for long )do not occur in humans.