This week, U.S. President Joe Biden blocked Nippon Steel's $14.9 billion bid to acquire U.S. Steel, citing national security concerns. The decision is seen as a major setback for the Japanese steel giant and has sparked heated debates on both sides. What does this decision mean for U.S.-Japan relations and the future of foreign investment in the U.S.? Could this signal a shift toward national security concerns being weaponized in U.S. trade policy against, not just its perceived rivals, but allies and partners too?