US stock futures drop, Nvidia tumbles on new curbs on chip exports to China | Reuters
1. Nvidia faces $5.5 billion in charges due to U.S. export curbs. 2. New curbs affect Nvidia's key AI chip sales to China. 3. Nvidia shares fell 5.2%, reflecting trade war concerns. 4. Wall Street futures down, driven by Nvidia and chip sector declines. 5. Escalating trade tensions may impact broader economic growth.