كتب : وكالات
The Americans now share the second spot in Group C with Cameroon on three points each, one point adrift of leaders Germany, who were held to a 1-1 draw by bottom side Korea Republic.
Bryan Arguez hammered the ball into the roof of the net just before the break to put the Americans ahead.
Cameroon found themselves two goals down just three minutes in the second period, with Tony Taylor drilling home from close range.
Dilly Duka widened the misery of Cameroon when he finished into the far post from an acute angle as keeper Francois Beyekol was anticipating a cross.
Banana Yaya pulled one back from the spot, but Brian Ownby restored the three-goal margin deep into the injury time.
Earlier on the same day, European champions Germany took the lead against the run of the play in the first-half but Korea snatched a deserved draw after the break.
Despite being forced into their half since the beginning of the game, Germany went ahead in the 33rd minute when Richard Sukuta-Pasu drilled a left-footer into the far corner.
Min Woo-Kim capitalized on poor defending from Germany in the 71st minute to grab the equalizer with a smart low shot.