BEIJING (Reuters) - American Express Co on Friday won approval to clear card payments in China, making it the first U.S. card network to gain direct access to what is set to be the biggest bank card market by 2020.The move comes months after Beijing started allowing foreign companies to apply for licenses and ahead of a G20 meeting in Argentina where the United States and China will try to resolve their trade disputes.The preliminary approval allows the company to process and settle payments in..