I feel as though there are 5 groupings of World Cup viewers. 1. The hardcore soccer fans who watch every game, or go to all their local team MLS games. 2. Those who watch many MLS and European games. 3. Those who know the big names and watch the occasional soccer game if nothing else is on. 4. Those who watch the World Cup because it is world class soccer at its finest. 5. Those who watch USMNT because 'Merica and who doesn't hate commies.
This is more aimed at the final two groups who may like watching the team play, but aren't as well versed in how the tournament will work.
For group play, all teams are garuanteed 3 games, against, you guessed it, those in their group. After those 3 games are done within their group, the top two teams (we'll get to how they are seeded in a minute) move forward to the knockout stage.
Teams that win a game, no matter the margin, are given 3 points. Teams that tie a game are given 1, and teams that lose are given 0. So, in the group stage if a team wins all three games they would get a total of 9 points. If they won two and tied another they would be given 7, and so on. If two teams are tied in points either between 1st and 2nd, and 2nd and 3rd, it goes to goal differential, or a teams net number of goals (goals for less goals against). If there is still a tie, then it will be on total goals, or total for. Then it will be the head to head result, followed by a random draw.
As Group G sits:
Germany - 3 pts +4 goals
United States - 3 pts +1 goal
Ghana - 0 pts -1 goal
Portugal - 0 pts -4 goals
In order for the United States to advance there are a few scenarios in which they would for sure be granted a spot in the next round and then a few with which they would need some help/ win by a big margin to move on.
If the United States wins their next two games, then they move on as the top of group and play the 2nd place team from Group H (Russia, Belgium, Algeria, South Korea).
If the United States tie the next two games giving them 5 points, then they would at least move on as the 2nd place team. In the other two games in the Group, Germany vs. Ghana, and Portugal vs. Ghana, if Germany were to either win, or tie they would go in as the first spot with either 7 points, or 5 as well winning on goal differential. If Germany were to lose, then Ghana could take the top spot if they also beat Portugal, with a total of 6 points. If Germany were to lose, and Portugal were to tie, then it would come to goal differential between Germany and Ghana. If Germany were to lose, and Portugal were to beat Ghana, then it would come down to goal differential between Portugal and Germany.
If Portugal were to beat the U.S. next game, then the U.S. would need to win against Germany, and depending on the results from Portugal v. Ghana, and Germany v. Ghana would either be sitting atop by themselves, or in a tie at the top and it would come down to goal differential.
If the U.S. were to beat Portugal, and lose to Germany, then either the U.S. would be in second behind Germany if they won, or tied in 1st with Ghana and Germany and would come down to goal differential again.
In essence, if the U.S. has a combination of wins or ties will move on to the next round. Any losses, and it does come down much closer. In the end, the win today sets the U.S. up well and controlling their own destiny.