The setup is absurd on purpose: aliens stealing color from the world, America immediately volunteering to save everyone with himself in charge, and the entire cast of personified nations scrambling to stop it. Hetalia commits to the joke instead of winking at the camera. You're watching Britain and France bicker while the apocalypse happens, and the show treats their petty arguing as the actual center of the world.
When a mysterious force sets off strange incidents around the world, the personified nations learn that Earth is being invaded by aliens from the planet Pict. The invaders want to drain the color from the world and turn every human into a Noppera, a faceless being with blank white skin and glowing antennae. Eight nations gather to plan a response but cannot agree. America wants to fight, England and France are still worn out from an earlier conflict, Japan cannot make up his mind, and Italy opts to surrender with a white flag. Each side then faces the aliens alone, and every attack fails while the white flag goes unheeded. America insists the world will be saved under his command. Forced back together, the nations decide their only chance to find the aliens' weakness is to sneak aboard the mother ship. The movie is a comedy in which the Allied and Axis nations must pool their strengths to save the planet.
