Anarchy Universalis
This mod makes it so that every country in the world starts with the Stateless Society government reform.
Newly released nations are pretty much guaranteed to become Stateless Societies as well.
However, there is one important change. The final tier of tribal reform allows the Stateless Society to reform into any government, not just a Republic. (AI will choose at random).
Personally, I recommend turning off Lucky Nations, for even more extra anarchy.
WARNING! Since many countries may choose to release subjects to cope with the lack of governing capacity, this mod may lower your performance, especially toward the start of the game.