The US quartet of Melissa Jefferson, Abby Steiner, Jenna Prandini and Twanisha Terry timed 41.14 seconds for a barnstorming victory at Eugene's Hayward Field.
Jamaica took silver in 41.18sec and Germany bronze (42.03). "This is the most fun race of my life!" said Steiner. "You can hear my voice.
I never scream that loud during a race." Anchor leg Terry added: "To be able to feel the energy from the crowd, to shake hands, sign autographs, it's just an amazing feeling. "The race was electrifying.
You heard the stadium. The stadium went crazy. We just brought it home." A loaded Jamaican team boasted newly-crowned individual 100 and 200m world champions in the shape of Shelly-Ann Fraser-Pryce and Shericka Jackson, as well as four-time Olympic sprint champion Elaine Thompson-Herah, 100m bronze medallist in Eugene, and Kemba Nelson.