TikTok is launching its Shop feature in the U.S. after mixed success in other countries. Meanwhile, Amazon’s Inspire feature brings short-form video to its shopping app. WSJ’s Meghan Bobrowsky on why the two companies are taking pages from each other’s playbooks.  Further Listening: -How TikTok Became the World’s Favorite App  -The Billionaire Keeping TikTok on Your Phone  Further Reading: -Amazon Confronts a New Rival: TikTok  Learn more about your ad choices. Visit megaphone.fm/adchoices