Lapira, who hails from Lake Charles, La,, and qualified to represent Ireland through his mother, Kate, became the first amateur player to play for Ireland in 43 years.
Lapira replaced Sunderland's Daryl Murphy four minutes from the end of the game, the first of two on Ireland's U.S. tour.
"I'm very excited," said the 20-year-old Lapira. "I wasn't as nervous as I expected to be. I didn't expect to play really and was just enjoying training with the team."
Lapira, who led all Division I scorers with 22 goals during the 2006 season and debuted with the PDL's Baton Rouge Capitals on May 12, joined the Ireland national team at Montclair State University in New Jersey last weekend for practice.
"When I first came into the squad," he said, "I thought the speed of the play was really ridiculous. What I'm used to isn't nearly so quick, and it's strange playing with stars in the team."
Ireland coach Steve Staunton was impressed with Lapira.
"He's come along," he said before the Ecuador game, "and he's done very well in training considering he hasn't had any football for the last two months."
Nicknamed the "Ragin' Cajun," Lapira is expected to train at Scottish club Aberdeen later in the summer before the start of his senior season at Notre Dame.
"This year is starting out where 2006 finished for Joseph," said Notre Dame coach Bobby Clark, who starred at Aberdeen.