Liverpool striker Firmino netted in the 11th minute at MetLife Stadium with a slick volley at the far post after Douglas Costa's blistering run and cross from the right.
Neymar was on target in Friday night's game against the US as he scored from the penalty spot just before half-time after Liverpool forward Firmino had given Brazil the lead. "I think just maybe a little nervous here and there", interim USA coach Dave Sarachan said.
The United States has two victories, two losses and three ties under the interim coach Dave Sarachan, who took over last October after the Americans failed to qualify for the World Cup. When Brazil defeated the United States by 2-0 at MetLife Stadium in August 2010 shortly after the site opened, the game drew 77,223.
Playing in New Jersey for the first time since its 2-0 loss to Costa Rica in a World Cup qualifier at Red Bull Arena last September, the USA did not force a save from goalkeeper Alisson until the 71st minute.
Brazil, in its first match since a quarterfinal loss to Belgium at the World Cup, improved to 18-1 against the USA and has won 11 straight since a 1-0 loss in the 1998 CONCACAF Gold Cup. The Americans were missing their top player, 19-year-old midfielder Christian Pulisic, who has an unspecified muscle injury.
The Brazilian player also revealed that, "I was the target of a lot of criticism, and I didn't feel well, When I'm not feeling well, it's better to keep quiet". Neymar's goal was his 58th in 91 appearances for his country.
Before the end of first half came Brazil's second goal when defender Fabinho cut into the penalty area, an action that led referee Fernando Guerrero to call foul.
However, earlier this week, Neymar insisted that he's making an effort not to be so theatric in the future.
Selecao coach Tite made a series of changes after the break, handing Arthur, Lucas Paqueta, Richarlison and Everton their first minutes in a Brazil shirt.