Editor's Note: This article is the fourth installment in an ongoing RANE series on the shifting patterns of global trade. The first installment provided a broad overview of the geopolitical and economic implications of these shifts. The second examined how recent changes to U.S. trade and tariff policies will affect nearshoring trends in Canada, Latin America and the Caribbean. The third assessed how rising tensions between Israel, the United States and Iran could impact shipping in the Strait of Hormuz. U.S. tariffs on South Korea and Japan could sway upcoming leadership contests in both countries, modestly increase their trade with China and erode U.S.-South Korea defense cooperation, but they are unlikely to undermine U.S.-Japan security ties. From April 16-18, Japanese and U.S. officials held trade negotiations in Washington, and South Korean representatives are expected to travel to the United States in the coming days to begin their own talks.