Thanks to their huge opening-match win against Ghana, the United States now has a 69.2% chance of advancing out of the group stage and into the round-of-16 knockout stage according to Nate Silver's World Cup model.
The United States' next match on Sunday against Portugal is a toss-up according to the model with the U.S. being given a 34% chance to win and a 37% chance to lose. The good news is that means the U.S. has a 63% chance of earning at least one point.
Assuming Germany beats Ghana, a tie against Portugal nearly guarantees the U.S. will advance. At that point, the best Portugal could do is tie the U.S. on points and the U.S. holds a big advantage in the tie-breaker, goal differential.