The United States' star sprinters flew and then flopped on the track while Belgium’s Nafissatou Thiam took heptathlon gold for the third time in a row.
On the track at the Stade de France, US sprint superstar Sha'Carri Richardson made up for her silver in the individual 100m with a gold-winning anchor run in the 4x100m relay.
Richardson turned on the afterburners to overhaul Britain, Germany and France in the home straight as the US quartet took gold in a season's best time of 41.78sec.
"The moment that I will describe is realising that when we won, the USA ladies, it was a phenomenal feeling for all of us," said Richardson.
But the US men again failed in their bid to win their first 4x100m gold since Sydney in 2000 with a disastrous baton fumble.
Already missing 100m individual champion Noah Lyles through Covid, a botched baton change completely slowed the US momentum, allowing Canada to snatch gold ahead of South Africa and Britain.
"You can never count us out, we feel great," said Canadian runner Aaron Brown.
Meanwhile, a nail-biting women's heptathlon saw Thiam become the first woman in history to win three consecutive Olympic golds, sealing victory ahead of Britain's Katarina Johnson-Thompson.
Thiam, the 2016 and 2020 Olympic champion, finished with 6,880 points after the 800m, the final event in the seven-discipline test of endurance.
Kenya's Beatrice Chebet won the women's 10,000m gold to add to her 5,000m title as defending champion Sifan Hassan finished third.
American Rai Benjamin outstripped Norwegian arch-rival and defending champion Karsten Warholm to win the 400m hurdles.
Spain's Jordan Diaz won gold in the men's triple jump leading a podium consisting of three Cuban-born men.
