The American quartet of Lauryn Williams, Allyson Felix, Mikele Barber and Torri Edwards tore around the Nagai stadium track in 41.98 seconds to pip the Jamaicans by little more than the thickness of a vest.
The Jamaican team of Sheri-Ann Brooks, Kerron Stewart, Simone Facey and Veronica Campbell took the silver in 42.01, just 0.03 behind the Americans, and bronze went to Belgium's Olivia Borlee, Hanna Marien, Elodie Ouedraogo and Kim Gevaert in 42.75.
Britain finished fourth and Russia fifth.
