4 ideas
Without warning, all planes, ships, broadcasts, and telecommunications between Iceland and the rest of the world stop, and no explanation ever arrives. As supplies run down, society slides from rationing and a flight back to farms and fishing into violence and an increasingly authoritarian nationalist government.
A wealthy society's comfort depends on continuous imports of food, fuel, medicine, and spare parts that its members never see. When the flow stops, the country falls to whatever its own land and sea can yield with the tools that still work, and that level sits far below its apparent wealth.
In a crisis, frightened citizens accept rationing, curfews, and suspended deliberation as temporary measures. Those who control the scarce resources soon find the emergency useful and never declare it over. Because each restriction is justified by survival, objecting starts to look like endangering everyone, so dissent gets reframed as treason.
As resources tighten, the definition of 'us' contracts, and those with the weakest claim to membership are marked as mouths the community cannot afford. Immigrants and outsiders are the first such group. Revived national myths and a romanticized self-reliant past supply the moral license for exclusion, turning a material shortage into an identity politics of who deserves to eat.