The Bryans, the top-ranked doubles team, have not lost a Davis Cup match since 2008. They were rarely troubled against a French pair that struggled to find any rhythm on the clay at Monte Carlo Country Club.
"We were ready for a dogfight," Bob Bryan said. "I thought we did a great job of not letting the crowd get too loud."
"Jo is capable of beating him," France captain Guy Forget said. "We're better ranked than them, so we have to go out and win."
Tsonga looked shaky at times when he beat the inexperienced Harrison in four sets Friday. Isner's huge serve and dominant forehand present a much bigger threat than Harrison's shot-making.
"He wanted to play on clay, now we must go and get the win. We all have our duties and responsibilities," Forget said. "It's a heavyweight contest between two big hitters."
On Saturday, the French pair lost their serve at the start of the first and second sets. The Bryans did not have to face a single break point.
The United States trailed 2-1 in the tiebreaker, but quickly rallied for a 5-2 lead.
Llodra's long forehand offered match point, which the Americans converted when Benneteau's backhand down the line sailed out.
"We both served at a high percentage, that's always key," Mike Bryan said. "We're good front-runners, so we played hard."
The tone was set from the start when Llodra's double fault gave the Americans the lead, even though France had been 40-30 up in the opening game. Mike Bryan's crisp volley made it 2-0 and Benneteau had to save a break point in the next game.
The last time the Bryans lost a Davis Cup match together was against France, four years ago, when Llodra played alongside Arnaud Clement.