Garcia scored on a power play with 46 seconds to go, rising out of the water to flip a pass from captain Jennifer Pareja past U.S. goalkeeper Betsey Armstrong and inside the near post. The goal capped a furious comeback for Spain after trailing by three goals with less than three minutes to play.
"That game was definitely a battle," said Kami Craig, who led the U.S. with four goals. "A lot of ups and downs in there but we'll take a tie and move on."
Spain, which is making its Olympic debut in women's water polo, controlled the first half and led 5-3 at the break behind three goals from captain Jennifer Pareja. But a veteran U.S. team cranked up its play on the defensive end in the second half, outscoring the Spanish 6-1 over to lead 9-6 with three minutes to play.
Undaunted, Spain roared back with Pareja's fourth goal of the contest and then two from Garcia to earn the draw.
"It's hard to hold Spain down for so long," U.S. coach Adam Krikorian said. "We played great defensively in the second half, besides the last two minutes. We needed to get a five-on-six stop there at the end and we couldn't do it."
With the draw, both teams remain level atop Group A with three points from two games.
The U.S. has stood on the podium at every Olympics since the women's game debuted in 2000, finishing third in 2004 and second in 2000 and 2008. With seven players back from the Beijing squad, the Americans are the gold medal favourite in London along with rival Australia.
For Spain, a draw against the U.S. provides a boost of confidence.
"This means that we're there with the best, our hard work is paying off. We're playing really good water polo," Garcia said. "We want the respect of other teams, we're a young team but I do think now that the other teams respect us because we showed them what we're capable of."
Ryan Lucas can be reached on twitter at www.twitter.com/relucasz