Read this: Whilst it is often perceived as an optimal solution for states comprising different cultural or ethnic communities, the federalist model seems to work best in largely homogeneous states such as the United States, Germany or Australia, but there is also evidence to the contrary such as in Switzerland. Tensions between territories can still be found in federalist countries such as Canada and federation as a way to appease and quell military conflict has failed recently in places like Lybia or Iraq, while the formula is simultaneously proposed and dismissed in countries such as Ukraine or Syria. Federations such as Yugoslavia or Czechoslovakia collapsed as soon as it was possible to put the model to the test.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): Where does the federalist model work worst in?
unanswerable