NEW YORK (AP) — A monthslong calm on Wall Street shattered Friday, and U.S. stocks tumbled after President Donald Trump threatened to crank tariffs much higher on China.The S&P 500 sank 2.7% in its worst day since April. The Dow Jones Industrial Average dropped 878 points, or 1.9%, and the Nasdaq composite fell 3.6%.Stocks had been heading for a slight gain in the morning, until Trump took to his social media platform and said he’s considering “a massive increase of tariffs” on Chinese imports. He’s upset a ...