Poor shooting stopped them from pushing Australia any closer, as they made only seven of 30 from the field in the first half, and finished 20 of 68 for the game.
Johannah Leedham and Rachel Vanderwal finished with 11 points each for Britain, while Natalie Stafford had 10. Lauren Jackson led Australia with 18 in the Group B fixture.
USA got the defence of their crown off to a winning start but were not as good as the final scoreline suggested in knocking off Croatia 81-56.
They extended their winning streak to 34 games dating back to 1992, but only after conceding an early lead and had to battle a determined Croatian side hard through the second and third quarters.
But as the game moved into the final stanza they began to make some defensive stops and break away for easy baskets, finishing the game on a 30-9 run.
Tina Charles led the way with 14 points, while Angel McCoughtry added 13 and Candace Parker 11 with 13 rebounds. Jelena Ivezic had 22 points for Croatia, with Marija Vrsaljko registering 19.
Meanwhile, China defeated the Czech Republic 66-57 to get the tournament going with an upset, while Turkey brushed aside Angola.
A hot start gave the Chinese a 15-4 lead over the 2010 World Championship runners-up, and although the Czechs closed the gap to 20-16 by end of the first quarter, China kept them at arm's length.
It was not until the third quarter that they drew level, 55-55, on Michaela Zrustova's three-pointer, but they looked to have little left in the tank as China finished on an 11-2 run to take the win in Group A.
Ma Zengyu led China with 16 points, while Miao Lijie added 12 and dished out eight assists. Eva Viteckova had 14 points for the Czech Republic.
The second Group A game of the day saw Turkey cruise to a 72-50 win over Angola.
In Russia's Group B opener, Becky Hammon scored eight of her 14 points in the final 2:40 of the game as they stormed back from a 10-point deficit in the fourth quarter.
Canada had led almost the entire game after cancelling out Russia's 10-3 start, and they were 50-40 up with 6:33 to go.
But after back-to-back threes from Anna Petrakova and Alena Danilochkina, Hammon tied it 50-50 and then took over in the closing stages.
France pulled away late on to beat Brazil 73-58 in Group B.
Celine Dumerc led France with 23 points and five assists. Erika Souza had 17 points for Brazil.