Strike Witches: US and Japan's arrival

Ever since the neuroi invaded, both Liberion and Fuso sent their witches and soldiers to fight against the aliens and once the threat is destroyed they will be able to return to their homelands as heroes right? No, the neuroi penetrated through Fuso and Liberion's airspace and permantly disintegrated those 2 nations, plunging the soldiers and witches of both nations to be retaliate with vengeance, that is until god filled with anger that his some of his children are killed by aliens retaliated by sending 2 similar, but alien nations to help the witches world.