The United States overcame a sluggish start to
110-63 in their second Group A match.
Tunisia started strongly, scoring two early three-pointers and, with his team trailing 13-12, USA coach Michael Krzyzewski changed his entire team.
They responded to surge into a 46-33 half-time lead and put on 39 points in the third quarter alone to end the chances of a major shock.
The win was enough to move the tournament favourites top of Group A.
Kevin Love and Carmelo Anthony both scored 16 points for the United States.
But Makram Ben Romdhane summed up the resistance of the Tunisian side, which had just two Europe-based players, by scoring a game-high tally of 22 points.
The United States, who started the tournament with a 98-71 win over France, are in action again when they take on Lithuania on Thursday.
NBA playmaker Tony Parker had 17 points and five assists as his team beat 2004 gold medallists Argentina 71-64.
Parker's team-mate at the San Antonio Spurs, Manu Ginobili, chipped in with 26 of Argentina's points.
France hit a 12-5 run in the middle of the final quarter to secure the game.