Firmino put the visitors ahead after 11 minutes when he tapped a volley home from close range after fine work on the right wing from Douglas Costa.
The goal was Neymar's 58th for his country in 91 matches.
Speaking to media Neymar Jr. said, "It's a great honor to be named captain, and I'll do everything to fulfill that duty and help the team win".
You can see Yedlin clearly asking the referee if he saw the World Cup in the video below. The new general manager, Earnie Stewart, said this week that a permanent coach would be announced this year.
Brazil's midfielder Douglas Costa came in from the right to make a cross at Firmino in a flawless center allowing the latter to send the ball past United States goalkeeper Zack Steffen, reports Efe news.
Neymar converted a penalty kick after a debatable call by Mexican referee Fernando Guerrero, the fourth official for US loss at Trinidad and Tobago last October that eliminated the Americans in World Cup.
The visitors were on top throughout against a young USA team that have been without a full-time coach since Bruce Arena resigned after they missed out on the World Cup finals for the first time since 1986.
Steffen kicked out his left foot in the 51st minute to save Neymar's 6-yard shot off a pass from Costa, and Miazga cleared the ball off the line.
Neymar, in turn, said he had accepted the armband "because I've learned a lot and I will learn much more, and this responsibility will be a good thing for me".
Arthur made his Brazil debut in the 60th minute, Lucas Paqueta in the 70th, Richarlison in the 75th and Everton in the 80th.