I always chalk up the US's wins to the superior team's underestimation.
Yeah, but the US players also had low expectations. There's no reason for it, actually. The same thing happened in basketball and hockey. Everyone expected the US team --with all the Dream players-- to roll over all the other world and Olympic teams. Then, a dream team lost ... they were outplayed by teams from South Am. and Europe. Soon, NBA teams were recruiting players from Argentina, Spain, France and Yugoslavia. This soccer win for the US was, imo, like that. It will (hopefully) inspire the players to think that they actually can play soccer at a world class level. And, there is absolutely no reason why they can not.
Maybe an even better example is cycling and Lance. I was a competitive cyclist and I remember that no one thought that Americans would ever be able to even compete with the Europeans. Then came Greg Lemond ... who got screwed by his team and later got shot in the ass by a relative. Still, he won the TDF twice. They said it was a fluke, until this guy named Armstrong came along.
So, I think that people do better overall when they ignore the expectations of others and expect the most from themselves. Or, as one old man used to say, "Never let someone else's opinion of you control your opinion of yourself."
"A man is rich when he has time and freewill. How he chooses to invest both will determine the return on his investment."