The Trojans, playing Penn State's style of smash-mouth football, outrushed the Nittany Lions 164 yards to 6, the lowest total for any Penn State team under Joe Paterno.
"People say I'm just a track star. They say, `Oh, he's fast, but all he can do is run track,'" said McCullough, a sprinter on USC's track team. "I want to show everybody I can do it all."
McCullough, who emerged as the starter in training camp, had 413 yards last season and never carried more than 21 times before getting 29 carries against Penn State.
Quarterback Carson Palmer also showed some toughness. Palmer, playing his first game since breaking a collarbone in the third game last year, was 10-of-20 for 87 yards.
"He handled the football team the way I wanted him to," Hackett said. "He handled the offense the way the leader has to. That was more important than how much passing he did."
It was the worst season-opening loss for Penn State since a 44-6 defeat against Nebraska in the 1983 Kickoff Classic.
The loss spoiled a homecoming for Penn State's Rashard Casey. The senior quarterback, who grew up in nearby Hoboken, played his first game since being charged with assaulting an off-duty police officer in May.
Casey was 7-of-24 for 106 yards. He was replaced by Matt Senneca in the fourth quarter.
"This was a tough outing for hifor a lot of reasons," said Paterno, who is starting his 35th season. "He had a tough preseason. Now that he has this out of his crawl, he can come home and have some fun."
Penn State came out tentative, and USC capitalized early. The Nittany Lions committed two false start penalties in the first three plays, then made a crucial mistake on special teams.
Safety Frank Strong, a late scratch from the starting lineup, burst up the middle and easily blocked David Royer's punt, and Sandy Fletcher returned it 6 yards to give USC a 7-0 lead just 2:15 into the game.
"A lot of these kids haven't played a lot of football," Paterno said, trying to explain the early jitters.
Penn State, which lost nine starters on defense, including Courtney Brown and LaVar Arrington, didn't seem like it had an overhauled defense early in the game.
An interception by Bhawoh Jue gave the Nittany Lions possession at USC's 38, and a late hit out of bounds by Ryan Nielson on Casey set up Ryan Primanti's 37-yard field goal that cut it to 7-3 with 7:37 left in the first.
But the defense couldn't provide any more big plays, and Penn State's offense, which was expected to be the team's strength, actually surrendered more points in the first half than the defense.
Troy Polamalu intercepted a badly thrown pass by Casey and returned it 43 yards to give USC a 20-3 lead with 2:37 left in the second. David Newberry missed the extra point.
It was the first interception returned for a touchdown against Penn State since USC's Quincy Harrison did it in 1994.
USC, which has struggled in games played on the East Coast, didn't seem affected by the cross-country journey. The Trojans played Big East-type football and pounded it at Penn State before a Kickoff Classic-record crowd of 78,902.
A 10-play, 73-yard drive capped by a 2-yard run by Petros Papadakis made it 14-3 with 1:44 left in the first. The drive consisted of three passes and seven runs, including five carries for 41 yards by McCullough.
"His tough runs over and over set the tone," Hackett said.
In addition to allowing touchdowns on a punt block and an interception, Penn State's offense committed five false starts, and gained just 87 total yards in the first half.
"Their defense really didn't do anything to disrupt us. We disrupted ourselves by jumping offsides and not getting where we need to be at time, and not making the right calls," Casey said.
The 393 combined yards were the fewest in Kickoff Classic history.
Paterno remains seven victories shy of breaking Bear Bryant's Division I-A record of 323.
©2000 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed