美股跌势扩大，标普500指数跌超1%，道指跌0.5%，纳指跌2%。

Group 1 - The U.S. stock market is experiencing a significant decline, with the S&P 500 index dropping over 1% [1] - The Dow Jones Industrial Average has decreased by 0.5% [1] - The Nasdaq Composite index has fallen by 2% [1]