Eddie Johnson, Landon Donovan and Mix Diskerud added second-half goals for the Americans, who will next play in Dallas on Wednesday against the winner of the Honduras-Costa Rica match.
Honduras and Costa Rica met Sunday night as part of a doubleheader before a sellout crowd at the home stadium of the Baltimore Ravens.
The U.S. has won nine straight full internationals - a record for the country's national team. The Americans have also prevailed in seven of their last eight Gold Cup matches, the exception being a 4-2 loss to Mexico in 2011 final.
Rodolfo Zelaya scored for El Salvador, now 1-19-7 all-time against the U.S.
Goodson put the U.S. ahead in the 21st minute by converting a crossing pass from Donovan, who gained possession near the end line within 15 feet of the net. It was Goodson's fifth career goal, the second in the Gold Cup.
Minutes later, U.S. goalkeeper Nick Rimando kicked aside a straight-on shot by Lester Blanco Pineda and batted away the subsequent rebound at the right corner of the net.
In the 29th minute, Corona gained possession at the top of the penalty area and used his right foot to line a shot into the left corner of the net for a 2-0 lead.
That drained much of the enthusiasm from the strong contingent of blue-and-white clad El Salvador fans.
The U.S. continued to dominate, and it took several strong saves by Dagoberto Portillo to keep El Salvador within striking distance.
Momentum shifted in the 39th minute, when El Salvador's Rodolfo Zelaya was fouled by DaMarcus Beasley and converted the penalty kick to make it 2-1.
Johnson added an insurance goal with a header off a pass from Donovan in the 60th minute. The score came 14 seconds after Johnson entered as a substitute.
Donovan converted a breakaway in the 78th minute. He is only player in history to score in six Gold Cup tournaments.
Five minutes later, as a sudden rain shower began to pick up intensity, Diskerud found the back of the net.