Juergen Klinsmann's USA side cruised past El Salvador 5-1 in their quarter-final at M&T Bank Stadium before Honduras edged out Costa Rica 1-0.
Landon Donovan scored and provided three assists for the USA, while Clarence Goodson, Joe Corona, Eddie Johnson and Mikkel Diskerud were also on the scoresheet.
The USA, favourites to win the tournament in front of their home fans, were lucky not to have conceded a penalty early against El Salvador after Goodson appeared to handle in the area.
And it was Goodson who opened the scoring in the 21st minute, putting away a Donovan cutback.
Nick Rimando pulled off a fine double save to keep the USA ahead soon after before the hosts made it 2-0 through Corona, who finished well into the bottom corner from the edge of the area.
Donovan should have made it 3-0 on the half-hour but he tried to be too clever with a chipped finish in a one-on-one with Dagoberto Portillo.
Klinsmann's men were dominant and impressed with some neat interplay in the attacking third.
They were made to pay for failing to take their chances when Rodolfo Zelaya was brought down in the area by DaMarcus Beasley after a mazy run.
Zelaya stepped up, producing a delightful 'Panenka' penalty as Rimando dived to his left in the 39th minute.
The tricky Zelaya was a constant threat for El Salvador before the USA restored their two-goal lead with Johnson heading in a Donovan corner on the hour-mark.
The USA took the direct route for their fourth as Johnson flicked on a Rimando clearance and Donovan raced clear, rounded Portillo and finished into an open goal.
Donovan's smart cross set up Diskerud for a fifth in the 83rd minute as the USA rounded out a huge win.
In the day's other game, Honduras moved into the last four thanks to Andy Najar's 49th-minute goal against Costa Rica.
Najar beat his marker to head in an Alexander Lopez cross and that was enough for Luis Suarez's side.