Brazil's Pix payment system has surpassed Visa and Mastercard in transaction volume, prompting a commercial investigation from the US Trade Representative. The system, developed by the Central Bank of Brazil, enables real-time money transfers between bank accounts with significantly lower fees than credit cards. The Brazilian government has defended the system, arguing it promotes competition and is available to all financial entities. The success of Pix has ignited a geopolitical and commercial battle, with the US supporting Visa and Mastercard.