Sports daily El Mundo Deportivo reported Xavi went to Iran three times while he was playing for Qatari club Al Sadd, and so needed to apply for special permission to visit the United States.
Xavi played the last game of his career in Tehran. Barca only realised they had a problem on Friday. They thought they had found a solution, but when they arrived at the airport, Xavi was not allowed on the plane and the team had to travel without him.
Reports said Xavi should be able to fly on Monday and arrive in Miami in time to lead the final training session before the friendly against Inter Miami on Tuesday evening.
Barcelona's recent signings Raphinha, Andreas Christensen and Franck Kessie all travelled with the squad. Robert Lewandowski told German television on Saturday that he would be joining the Barcelona squad on the tour.