U.S. stocks dropped as the costs of U.S. restrictions on global trade compounded. The S&P 500 fell 2.2% Wednesday. The Dow lost 1.7%, and the Nasdaq composite sank 3.1%. Losses accelerated after the Federal Reserve’s head said President Donald Trump’s tariffs could push economic growth lower and inflation higher than earlier thought. Nvidia sank after saying new U.S. restrictions on exports to China will chisel billions of dollars off its result…