That game unfairly gets pegged as Garcia having some kind of miracle game. Granted, he had a very good game, but it was one of 4 very good games in a row he played. He actually had a better game statistically the week before vs auburn, and then threw for more yards the next two weeks. It's unfair to Garcia & USC to say Bama just caught him on a hot day, they really caught him in the midst of a hot streak. Over a 4-game stretch he went 83 of 112 (74%) for 1173 yds & 10 TDs. Those numbers don't seem great by today's standards, but in 2010 at USC (which was surprisingly a running team under Spurrier), those were outstanding numbers.
That 2010 game was lost simply because Bama did not run the ball well and USC did run the ball well (at least they ran it well enough) and Bama had some kicking woes (missed short FG, missed extra point, 15-yard punt), plus Bama had no answer for Alshon Jeffery who averaged 18.1 yards per catch. He and Lattimore were arguably more damaging to Bama than Garcia, who threw several jump balls that Jeffery was able to come down with. Lattimore had a business-like 93 yards rushing & 16 yards receiving with 3 TDs.
If there was a key play in the game it was McElroy's fumble. Bama had the ball near midfield, 1st & 10, down 14-3. Had they scored there it's 14-10 or 14-6 and possibly a different game. Instead, McElroy is sacked and fumbles & USC takes over with great field position and scores to go up 21-3. At that point Bama was playing uphill much of the rest of the game.