Spain came close to causing a sensational upset as they ran defending Olympic Games champions Todd Rogers and Phil Dalhausser close before the USA team booked a place in the last 16 of the men's competition.
Pablo Herrera Allepuz and Adrian Gavira Collado looked set to spring a surprise when they took the first set 21-19 but order was soon restored at Horse Guards Parade.
Rogers and Dalhausser stepped it up a gear in the second set and raced into a 13-6 lead with some aggressive play at the net, eventually winning it 21-16.
The Spaniards, who won their opener against the Czech Republic, battled hard in the decider but despite saving a match point, they lost the next one to go down 15-13.
Meanwhile, Emanuel Rego and Alison Cerutti resumed normal service as they eased to their second Pool A victory.
Brazil's number one team were forced to battle from a set down to win their opening match against Austria, but looked much more assured today as they dispatched Switzerland's Patrick Heuscher and Jefferson Bellaguarda in straight sets to make sure of their place in the knockout round.
The intimidating frame of Alison proved an insurmountable barrier for the winless Swiss during the 36-minute contest, and the South Americans' 21-17 21-12 win was never in doubt.
The Czech Republic overcame Japan 2-1, while Latvia enjoyed a 2-0 win over Venezuela.
The Netherlands defeated Germany 2-0 and Austria won by the same scoreline against Italy.
In the women's competition, Brazil's Talita Rocha and Maria Antonelli showed all of their battling qualities as they beat down the determined challenge of Germany's Sara Goller and Laura Ludwig in three sets.
In a 66-minute encounter, Brazil's second-string duo recovered from the disappointment of losing a titanic 60-point second set to prevail in the decider for a 21-19 29-31 15-13 win.
Spain were too strong for Argentina, winning 2-0, with the Netherlands overcoming Australia by the same scoreline.
Italy overcame GB 2-0 and Russia edged out Canada 2-1. The USA were 2-1 winners over the Netherlands.