Your question strikes at the heart of what has driven much of traditional folklore studies since the Jacob Grimm began his work two centuries ago. Initially, this question was at the fore because people wanted to understand how a folktale changed as it drifted through time and space. The presumption was that to understand how it changed after jumping over various geographic boundaries, it would be possible to trace it back to its "Ur" form, the very first telling of the story. But this ambition was fraught with problems and yielded little by way of satisfactory answers after a great deal of work.

That did not make the core of your question any less relevant. Interest remained in how folklore diffused and was affected by that diffusion. What emerged was an understanding that differences in core beliefs and other conditions, defined geographically, affected stories. Generally, the boundaries in question were far less sharp than what one finds in linguistic studies, but the boundaries nevertheless existed - at least to a certain extent.

For example, traditionally, western Europe had a belief that people could transform into animals (and that animals could occasionally take the form of people). A motif that appears in a number of folktales involves a hero who befriends a number of animals (usually three) on his journey. As thanks, each animal bestows on him the ability to transform himself, and he uses these forms to overcome the issue that is at the core of the story. As the story drifted east into cultures that did not believe in this sort of transformation, the animals bestow on the hero a hair, feather, etc., and the hero understands that if he finds himself in a tight pinch, he merely needs to rub the token to summon the animal - which then performs basically the same function for the hero.

Another example: Northern Europe has the idea of social supernatural beings who live in families and village groups. These fairies (or entities with other names) are unusual internationally. Their counterparts in eastern and southern Europe tend to be solitary (or appear in twos or threes, but they nevertheless function as a single unit). When a northern supernatural beings abducts an infant or a woman who is about to get married or has just given birth, the abduction is typically carried out by a number of these entities for the sake of their community at large. Elsewhere, the abductor is usually a single entity who steals the human for her own purposes and satisfaction.

It is possible to document variants of folktales and legends as they jump these boundaries and transform. I have completed a study along these lines with Cornish folklore (my book manuscript is currently in review, but I have also published three separate articles on this issue). In this case, I have been able to document how folktales and legends that diffused into the remote Cornish peninsula frequently transformed in response to the maritime environment. Horses were replaced by boats, and the change from a terrestrial to a maritime setting changed other details of the stories. Here the boundary may be more precise geographically, but it is difficult to say since the southwest of Britain lacks the sort of extensive collecting that one finds in Ireland and Scandinavia.

Speaking of which, the Irish have done excellent work in mapping various motifs as they appear (and don't appear) in various places in Ireland. For example, Patricia Lysaght's excellent study, The Banshee, documents various attributes of this specialized supernatural being as they appear in restricted terms geographically.

So the answer to your question is yes, there are these sorts of boundaries, but they tend to be less sharp when compared to linguistics. I should also note that I have worked on the problem of defining historical boundaries - shifts in the oral tradition that occurred because of temporal boundaries. Conversion to Christianity and the introduction of industrialism and corporate ownership of companies appears to have affected at least some stories and traditions in a way that is analogous to vowel and consonant shifts.

I hope this helps.