NEW YORK — What might have been a straightforward, celebratory moment amid a landmark summer for American Taylor Townsend instead became a heated meeting at the net Wednesday at the U.S. Open.

arch wasn’t the best month to be a billionaire, as both the S&P 500 and Nasdaq sank by nearly 5% amid the Iran war. Nine of the world’s ten richest people enter April poorer than they were at the ...