"The way Texas was raming the ball down USC's throat at the time, they would surely have scored on the next few plays and probably would have nailed the extra point." You don't know that. They could have, at best, wound up with a FG, the same way SC stopped them in the previous drive. And since he just missed the extra point it is just as likely he would have missed a FG. We'll never know. Agreed, though, the way Texas came back from 12 points down was impressive.
Exactly my point, there are many "ifs" that could have change the course of the game. What really counts is what happened on the field after USC was leading by 12 points near the end of the game. Texas won - by a "whisker," because they sucked it up and grabbed the lead before the clock ran out of time. If there been more time, the pendulum may have swung back to USC - but that is another "if."