For millions of people in the U.S. who use the Chinese app WeChat, it’s a lifeline to friends, family, customers and business contacts in China. That lifeline is now under attack by an executive order from President Donald Trump that could ban the app in the U.S. as early as mid-September, potentially severing vital relationships. In China, WeChat, or Weixin as it’s known, is critical infrastructure — texting, social media, cab-hailing, payments and more, all wrapped into one app. For people in the U.S., WeChat has less functionality than it does in China. But it’s what connects immigrants and students from China to their pasts and to each other.