France, the defending champions, had won their last three fixtures against the Irish but managed only a solitary Damien Penaud try, while the hosts, world ranked number one to France's two, scored four for a bonus-point victory.
"We deserved the defeat, we were overwhelmed in important moments," Galthie said. "We were close for a long time but could not bridge that gap and the Irish managed to keep us in our half.
"We have to admit that the best team won and this game will give us a lot to analyse and keep us ambitious. Today was a defeat and we'll have to analyse and learn from it.
"It's high-level sport. You have to be able to bounce back and get ready for Scotland in two weeks."
Scrum half Antoine Dupont (26), who made one incredible defensive contribution when he somehow wrestled winger Mack Hansen backwards as a try looked certain, added: "Physically and strategically, it was tough.
"Every little mistake gave our opponents chances to score. It was very intense throughout.
"It's very disappointing because they got a bonus point and we didn't. We played a big game but lacked precision and failed to score in our strong moments. We'll have to recuperate and go on with this tournament. We're not giving up."
Lock Thibaud Flament (25) said: "It was a tight game, we knew it would be hard, they're in good shape and world number one.
"We're frustrated but it was a great game. We put in a lot of heart and effort so there's nothing to be ashamed of. We just need to be a bit more precise in our half."
France's next game is at home to Scotland in two weeks but of greater interest might be a potential quarter-final rematch with the Irish at the Rugby World Cup later this year.