When people across different continents and cultures experience the exact same dream entity, there are usually two main explanations that bridge the psychological and the esoteric.
First is the collective unconscious. Certain figures, like a 'dark person' or shadow figure, are primal human archetypes. They aren't bound by modern culture because they stem from our deepest instinctual psyche representing the shadow self, the fear of the unknown, or unintegrated aspects of the mind.
Second, from an occult standpoint, the astral plane has no physical geography. If you are dealing with an actual external entity or a massive global egregore, physical distance means absolutely nothing to them. They can access the dream space of multiple people because they operate on a non-physical frequency. When sensitive individuals around the world tap into the same current, they will perceive the same entity, even if their personal brains translate the visual details slightly differently.