How many of your subscribed communities lie outside of lemmy.world? Very possible you've pigeonholed yourself. World almost certainly has a heavy US bias as it was the largest instance with open registration during the exodus.

Lemmy is made up of a ton of instances, many of which have quite limited US-related content. Posts from smaller instances may not rise to the top of World but they do elsewhere. Whereas World posts are going to rise across most instances, due to sheer volume. Where the posts come from is not as indicative of diversity as where the comments and votes come from.