Tbf, the lemmy.world politics community does have rules stating US-only posts. They could have chosen a better name, but they didn't. World news doesnt have any such rules so it's hard to know if their intent was foreign affairs related news between various countries or just news from around the world. Until they clarify, folks will likely interpret how they wish, and unfortunately it looks like that's gonna lead to a bunch of US centric news (based on observation, though I don't know why). Posting it in politics or uspolitics would reach a better audience, but folks are gonna do what they do.