Temu and Shein have exploded in the U.S. by going on an online marketing blitz and offering consumers inexpensive goods from China, whether it’s a $3 pair of shoes or a $15 smartwatch. The rise of the discount shopping apps, along with TikTok Shop from China’s ByteDance, have generated fresh competition for U.S. e-commerce companies Amazon, eBay, and Etsy. Much of their growth, is the result of a trade loophole, known as the de minimis exception.