I think three things combined to change the game around. 1)You really had USC in a miserable place late in the half, and putting up one more score just before halftime could've been huge, considering you received to start the 2nd half. 2) The fumbled punt, and 3) If I'm a coach and my opponent is looking to pick up 4th & a foot I know I'd be in a tough position to stop it, but my hopes would be buoyed at least a little if the opposition lined up in a shotgun. Not that I was particularly surprised because we've done that before.
Overall, this staff needs more time before they're deemed a failure. But there are instances, including today, that point directly at some real issues regarding discipline & smart play. I thought they played hard today, they're playing more physically than before, and given the talent they faced at the offensive skill positions I felt the back end competed pretty well most of the time. It was no surprise the defense would run out of gas near the end given that the offense isn't exactly built to keep them off the field.