After three days of competition, the sporting superpower has just three golds and is struggling to build momentum. At the same stage four years ago in Sydney, Americans had already claimed six Olympic titles.
Of course the United States are still confident of ending up top of the medals table as they did at the 2000 and 1996 Games. Their strength in track and field will not be felt until the second week of the 16-day Games.
So far, though, U.S. sports fans have seen their mighty basketball team humbled by Puerto Rico and teenage swimmer Michael Phelps fall at only the second hurdle of his much-hyped attempt to claim a record eight gold medals in a single Games.
Phelps also failed on the third leg of his campaign for gold on Monday, collecting a bronze in the high-profile 200 metres freestyle.
SWIMMERS STRUGGLE
In the pool, the U.S. team has failed to live up to its billing as the strongest since the 1976 Games in Montreal.
The men recorded America's worst ever showing in the 4x100 freestyle relay on Sunday, claiming only bronze as South Africa won with a world record and the Netherlands took silver.
The women's team, which won the last three Olympic 4x100 metres freestyle relay titles stretching back to Barcelona in 1992, had to settle for silver this time behind Australia.
One of their biggest individual hopes, Katie Hoff, failed to reach the final of the 400 individual medley.
Aaron Peirsol and Natalie Coughlin provided balm for wounded U.S. pride with victories in the men's and women's 100 metres backstroke finals on Monday night.
However, their achievements will do little to erase the shame of a national basketball side filled with NBA players losing by 19 points to Puerto Rico, an island of just four million people.
"We couldn't hit a shot to save our lives," said New Jersey Nets forward Richard Jefferson.
Ironically, Americans' past success may have sown the seeds of their current difficulties. American sports idols marketed around the world have inspired people far and wide, and many flock to American teams and universities to learn their trade.
"No doubt, Michael Jordan was an idol. We all tried his moves on the playground, and we all watched the Dream Team play in 1992. We all wanted to be like them and this is the result," said Carlos Arroyo, the Puerto Rican guard that shredded the Americans with his ballhandling and pressure shooting.
Americans are still winning medals, but they are tending to be silver and bronze. In the men's gymnastics team final on Monday they finished second behind Japan, who won their fifth gold. China lead the medals table with 10 golds.
Dain Blanton and Jeff Nygaard exemplified the American experience over the first three days. The team's top hopes for a medal in men's beach volleyball, they lost their second straight match, which makes it virtually impossible for them to move past the preliminary rounds.
American men have won gold in beach volleyball in 1996 and 2000 -- since the sport debuted as a medal sport -- but it doesn't look good this time.
