i do history extension!! i guess the thing to keep in mind is make sure you're analysing the creation of history not history itself - like i don't know much about the Mayan decline but you could talk about the proposed theories and the historical evidence behind them and the historians purporting them, i.e. potential motivations a historian might have to back that theory.
i really don't know other than that! not very familiar with south american history unfortunately. i'm doing mine on the boundary between history and fiction, and how we define ancient works, that may be more fictive. my case study is plutarch on alexander the great
idk if that helps but my proposal got full marks so i guess it's an okay basis?