ByteDance Ltd.’s TikTok is back on US mobile stores and the app that seemed poised to take its place has suffered a precipitous drop in interest.In the five days following TikTok’s relisting on Apple Inc.’s iPhone app store and Alphabet Inc.’s Google Play, downloads of social app Xiaohongshu plummeted by 91%, according to Sensor Tower data. Also known as Rednote, the social app is commonly referred to as China’s version of Instagram and boomed in popularity when TikTok’s potential US ban approac...