The 35-year-old Bryan twins beat the British duo of Colin Fleming and Dominic Inglot 6-2, 6-3, 3-6, 6-1 outdoors at Petco Park in San Diego, pulling the Americans to within 2-1 in the best-of-five event.
The United States must sweep Sunday's reverse singles to advance to the April quarterfinals. The tentative schedule calls for world No. 6 Andy Murray to play Sam Querrey with Donald Young meeting Briton James Ward.
Britain had grabbed a 2-0 lead In Friday's opening singles as Murray dispatched Young and Ward rallied to overcome Querrey in five sets.
The winner will go to face either Argentina or Italy in April's quarterfinals.