I'm not going to analyze the game because my co-contributors have already done so and there are a plethora of analyses elsewhere too. However, I do want to comment on how thrilling and satisfying a victory this was.
There's been a lot of discussion on where this victory ranks among the greatest US upsets. I'm certainly not old enough to speak to the 1950 victory over England, but I have witnessed all the victories since the 1994 World Cup. As an overall performance, this ranks up there as maybe the best (Colombia was beaten on an own goal, the first half against Portugal in 2002 was great, but the second half was a matter of hanging on by a thread, beating Brazil in 1998 was basically the result of one man - Kasey Keller - playing out of his mind).
The Portugal game elicited a pure joy because it was so stunning to go up 3-0 and it was so unexpected - the US was coming off the 1998 World Cup debacle, Portugal were heavy favorites, etc. The subsequent dos-a-cero against Mexico in the second round was not as thrilling but possibly more meaningful and brings greater joy to this day, at least personally, because it was a victory over our hated rivals on the biggest stage possible. This match didn't carry the significance of the World Cup and I think more is expected of the US than in 2002 (at least within the US soccer community). But the joy is just as great because of the who and how - the US beat the unquestioned number 1 team in the World, a Spanish side that is absolutely loaded from top to bottom, and the US tried to attack with purpose and produced good football. Furthermore, the heart and grit and determination was simply amazing, and it just makes me proud to support a team that can turn around its form within a week and produce such a display.
Unfortunately I had to watch the match from my office via ESPN360, and I missed out in sharing the experience at the side of fellow fans. But even just exchanging texts, IMs, and emails during the match, and the responses after the final whistle, you could feel connected to everyone else who was watching and could revel in the victory together as a community of fans having witnessed a moment that epitomizes why we are fans of sport in the first place, and of the beautiful game in particular.
On a side note regarding ESPN, there are many reasons to decry their coverage generally (and more specifically, how bad is their primary broadcast team, JP Dellacamera in particular) but I was happy to see the US victory as the lead story on ESPN.com and SportsCenter. Of course ESPN had to run a poll asking whether this victory made you care more/less/the same about US soccer. I hate those stupid polls because it just reinforces the idea that people don't care in the first place, but all those voters who say they will pay more attention to US soccer and the World Cup in the future, well I suppose I can only hope it turns out to be true.