At the top of the medal table, they are almost equals. To almost universal surprise, China is mounting what could be the strongest challenge to the United States' gold-medal supremacy since the dissolution of the former Soviet team a decade ago.
With the Games going to Beijing in 2008, the ramping up of the Chinese Olympic effort looks as if it could mark the emergence of a new Olympic power - and the rival that the United States has been lacking.
China is legendary for plucking young athletes and putting them though rigorous training. And its medal count in recent summer Games has shot upward, with no sign of leveling off.
Just don't expect to see all these athletes on NBC. So far, the success of the two nations seems to be mutually exclusive - each dominates events in which the other falters. Part of that is by design, as the Chinese seek to bolster their medal totals by targeting sports where competition is thinnest.
There is also a significant sporting disconnect between the two countries. While track has no tradition in China, for example, badminton only gives Americans a hankering for barbecue. The result could be a rivalry only on paper, as the two nations compete for control of two very different Olympic Games.
Most nations tend to do better in those Games before and after the one they host, says David Wallechinsky, an Olympic historian. "But [the Chinese are] doing particularly well."
Hidden high in the piney shoulders of a hill above Athens, the Goudi Olympic Complex gives a foretaste of 2008. In an event that didn't even make NBC's 1,210 hours of Olympic coverage, the women's doubles badminton semifinals are about to begin. On the court in the first match is a team from China against a pair from South Korea. The second semifinal includes another team from China against a third Chinese duo.
There is not an American flag in the building, but in between points, the seats are a sea of Communist red and the rafters rumble with a cheer roughly translated as "China! More energy!"
These are the Olympics from a Chinese perspective. Swimming and track are on the fringes of the country's consciousness. The serious business happens here. And at table tennis. And at diving.
A glance at the medal tables shows the contrast. America finished with 28 medals in swimming; China had two. China took 11 medals in badminton and table tennis; the US none. With minor exceptions, the only sports in which America and China both compete well are gymnastics, diving, and shooting - though even those rivalries have failed to materialize in these Olympics.
By 2008, some of that could change - particularly on the Chinese side. Asked what China can do to improve its medal chances in Beijing, the vice president of the Chinese Olympic Committee launches into a five-minute answer that is lacking only an accompanying PowerPoint presentation.
He knows every detail of Chinese Olympic success and failure. The country has fared poorly in team sports. Its medals come from a few core events. It qualifies far fewer athletes for finals than either the United States or Russia.
"The first step is to push into the first eight places and bridge the gap between China and the world's sports powers," says Duan Shijie. "We must increase participation in all sports."
On a recent day after the platform diving semifinals, the two Chinese divers - ages 16 and 17 - are the only ones who remain after the competition. Even though they have put in some of the best performances, they stay more than a half hour, taking direction from their coach and making more than a dozen practice dives.
The mortar of Chinese success is hard work. Still, even with a huge national effort, some say it will be easiest for China to pick off events on the periphery, where the talent pool is not as deep. "It's so hard to break into track and field," says Mr. Wallechinsky. "They're so far behind."