Most of us here understand how big a US victory in the World Cup would be. For the uninitiated, the US is playing Ghana tomorrow (sad for me; my parents-in-law just came back from 18 months there and it’s a wonderful nation) and must win and have Italy beat the Czech Republic in order to advance to the second round.
Unfortunately, the US performance could end up being directly correlated to a bad result in the other game. To wit:
Italy does not need to win. A tie guarantees them to go through. The good news here is that Ghana could still win the group, so Italy has to play for the win or face Brazil in the next phase. So Italy comes out playing for the win, but the stronger the US performance, the less incentive there will be for Italy to press for it. If the US wins, Italy needs only a tie to win the group.
Czech Republic also do not have to win to go through. In fact, beating Italy seems quite unlikely, and pushing to do that leaves CR open to defeat, which puts the next round seriously in doubt. Therefore CR will come out early looking for the tie, and will watch the scoreboard closely to determine whether tactics have to change. Unless the US beats Ghana by 4, they are in no danger from us. Again, the stronger we are, to a point, the less hard CR will push for the win.
Worst case scenario: US comes out and scores a quick goal, but nothing else for 30 minutes. This practically guarantees a listless, draw-oriented match in the other game.
Best-case scenario: US scores 5 goals in the first 5 minutes. CR then has to play for the win, and Italy have to respond or face the possibility of losing out altogether.
Likeliest scenario for a US second-round berth: Ghana scores an early goal. This forces both CR and Italy to play for the win. Neither wants to play Brazil, and playing for a draw with the risk of losing could cost them the next round altogether. Italy is likely to be more successful at this, and should get a goal or two. Then the US scores in the 80th and 91st minutes and wins the game. Italy beats CR 2-0.
Likeliest scenario considering that the US will likely have to score more goals in this game that it has SHOTS on goal so far in the entire World Cup: Ghana gets a goal in the first half and scores again on a quick counter late in the second, while the US manages a goal at some point. Italy and CR play to a 1-1 draw.