The Fire Nation replaces Japan on July 1853 right before Commodore Perry arrives to force Japan to trade with them. This occurs after Republic city is created. Also for whatever reason Aang, and the rest of the Gang are there. How would Zuko react to being in a new world and meeting Perry and his forces? How would Perry react to finding Japan replaced and seeing the locals control fire and learning about the Avatar?
What will the Fire nation do in this new world, and how would its new neighbors respond?