Brazil is a politically divided country, but there's one thing that those on all sides of the political spectrum love: PIX, the country's instant payment system that allows users to pay for everything, from ice cream on the beach to clothes in a shopping mall and even a car. Unlike payment apps run by private banks, PIX is governed Brazil's Central Bank. Its massive popularity drove $7 trillion in transactions last year, though now it faces scrutiny from the U.S. government over claims of unfair trade practices for bypassing traditional credit networks like Visa and Mastercard. “The best (payment method) is PIX, the most used,” said Luis Felipe de Almeida, a 21-year-old vendor of iced tea and cassava starch biscuits on Ipanema beach in Rio de Janeiro.…