US markets today: Wall Street logs second sharp fall as AI favourites tumble; global indices mirror tech-led slump

US stocks extended their sharp decline on Friday, with Nvidia and bitcoin-linked plays leading the losses as the S&P 500 headed for a second straight heavy loss. Global equities mirrored the slide, with Asian and European markets deep in the red due to renewed anxiety around AI valuations, interest rate expectations, and China’s economic slowdown.