美股跌势扩大，道指跌2%，标普500指数跌1.75%，纳指跌1.64%。

Group 1 - The U.S. stock market is experiencing a significant decline, with the Dow Jones Industrial Average dropping by 2% [1] - The S&P 500 index has decreased by 1.75% [1] - The Nasdaq Composite index has fallen by 1.64% [1]