If this goal doesn't happen, Americans go back to not caring about soccer for the indeterminable future, and who knows how much longer it takes for the sport to gain real and serious ground in the United States? We'll follow and support national teams as long as they're winning, but as soon as they start losing or otherwise choke (and a tie to Algeria most definitely would have been classified as one of those) we go back to watching Wipeout and wishing (real) football would start.
As it is, Landon Donovan kicks the ball in the net and we care about this sport for at least another few days.
Also, I find it interesting that the two most important goals for the U.S. came when the opposing goalie was unable to fully control a save. Not sure how frequent an occurrence that is, really, but in general I like it when the team I'm rooting for actually beats their opponent, rather than the opponent beating themselves. This feels kind of cheap. Maybe I'm way off base here, though.