Asklemmy

If by "diverse" you mean "has western conservatives", then considering how the entire concept of the fediverse is progressive, you're not going to find many of them here. On Reddit, there's r/AskPolitics which overall leans liberal and is US centric but is more open to discussion than other subreddits. There's some other debate subreddits as well which you might be interested in. They're helpful for developing political views, but after that hearing the same BS from people who have fundamentally different values gets tiring and people leave so that's why there aren't many of those spaces.

If you're open to other viewpoints that are opposed to both Republican and Democrat, leftist instances like lemmy.ml, Hexbear, Lemmygrad, and dbzer0 have that, and they can have very different stances on other issues as well (i.e. Lemmygrad vs dbzer0). They can still be echo-chambery (which is hard to avoid) but they also tend to have more users that are interested in intellectual debate.

As far as what instance actually has the most diverse points of view, I'd say lemm.ee which federates with basically everybody and I've seen users there from all over the political spectrum. However, there's isn't much in terms of political discussion there compared to other instances.