I have been asked how the World Cup field is determined so I figure I will summarize it the best way I can.
First of all, the host country, South Africa, automatically is in the tournament. The other 202 countries who entered played starting in August 2007 for the remaining 31 spots within their region of the world. 13 from Europe, 4 from Asia, 5 from Africa, 4 from South America and 3 from North/Central America make the field. The other two spots are determined by a playoff between the first non qualifier from North/Central America and South America regions along with the first non qualifier from Asia playing the Ocenania region winner.
For the United States, they had to qualify as one of three teams from 35 countries in the region. Seeded as one of the top 13, they did not have to participate in the first round where 22 teams played for 11 spots. The 11 advancing teams played a head to head match with one of the 12 seeded teams and the 13 seeded team played a match against one of the top 12. The US defeated Barbados 9-0 total goals in two games to advance.
The third round had the 12 teams play in three groups of four round robin home and away (6 total games per team) and the top two teams from each group advanced to the region final. Those 6 teams played another round robin home and away match (10 games per team) finishing last October 14 where the top three (US, Mexico, Honduras) made the final and the fourth place team (Costa Rica) went into a playoff with the 5th place team from South America (Uruguay) which Uruguay won. The United States had to play 18 total games from June 15, 2008 to Oct 14, 2009 with a total record of 13 wins, 3 losses and two ties to qualify for the final.
The 32 teams are seeded in four groups of 8 and one team from each group by random draw is placed in one of 8 groups of 4 as shown here:
The teams in each group play one match agains the other three teams and the top two advance into a 16 team single elimination format where the champion is crowned on July 11th.