The implementation of 25 per cent import tariffs on Japan and South Korea by the United States starting August 1, 2025, marks a historic shift in international economic relations. This policy choice simultaneously targets two key security partners while putting at risk the supply chain networks built over many years of economic integration.

The research shows that the rapid tariff increase will create immediate industrial damage, especially in the automotive and semiconductor sectors, along with significant disruptions to worldwide trade patterns and Northeast Asian strategic movements and damage to the liberal international order after World War II. The research evaluates the multiple problems created by Washington’s unilateral move by using 2025 trade statistics and cost analysis projections to analyse the long-term effects on regional stability and economic governance.

The two nations trade a substantial amount of goods each year, which will lead to severe market disruptions when trade barriers are applied. In 2024, the United States received goods worth USD 148 billion from Japan , while South Korea supplied USD 66 billion, which positioned both countries among the top seven importers in the U.S. The automotive sector represents more than 30 per cent of Japan’s U.S. exports, which translates into annual exports of USD 44 billion before the sudden imposition of a 25 per cent tariff. The United States bought more than USD 18 billion worth of semiconductors from South Korean manufacturers during the previous year, and South Korea maintained its position as the world’s second-largest semiconductor supplier behind Malaysia. Companies in these industries operate based on just-in-time delivery systems , which depend on the free movement of parts between the U.S. and Japan borders five times throughout the manufacturing cycle. A tariff shock of this magnitude, therefore, entails cascading cost increases: preliminary........

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