Jermaine Jones broke the deadlock with his first goal for his country four minutes into the second half after his shot took a deflection off Jamaican defender Jermaine Taylor, giving goalkeeper Donovan Ricketts no chance of making the save.
"I thought we played a good game today," U.S. coach Bob Bradley said. "It took a while to get the goal and the second goal, but certainly as far as establishing our game today I thought we did an excellent job."
American striker Clint Dempsey, who rejoined the team on Sunday after missing three days to attend his sister's wedding in Texas, put the result beyond doubt in the 80th minute, side-stepping an advancing Ricketts and tapping the ball into an open net after a low cross from Juan Agudelo.
Landon Donovan, who also missed three days of training to attend his sister's wedding in California, started the game on the bench.
"There are times that players come to you with personal requests," Bradley said. "Ultimately, after speaking at different points with Clint and Landon, I knew how important both of these days were for them. You always try to do what's best for the team and you make tough decisions."
Mexico and Honduras will play in the tournament's other semi-final.
"As the tournament goes on, you start to build team unity. It doesn't happen right away," said Donovan. "We're starting to play as a team. Tonight was a really good performance."
