Florian Wirtz scored Germany's fastest international goal after seven seconds before the Euro 2024 hosts doubled their lead early in the second half through Kai Havertz to earn victory in the Lyon friendly.
"I think we were outclassed in every department," Tchouameni told French TV network TF1.
"We couldn't put our game plan in place. We came up against a great team. We need to do better, individually and collectively.
"It's a wake-up call, but there's no need to overreact either. We are aware of and confident in our qualities."
Striker Olivier Giroud said France could make no excuses for the defeat, telling L'Equipe: "We started the game badly, they caught us cold, we were slow to react and we didn't score at our best.
"In midfield, they tended to find their players between the lines. It's a reminder that you need to be in the thick of things from the start and for 90 minutes."
France next face Chile in a friendly at the Stade Velodrome on Tuesday.
Euro 2024 runs from June 14 to July 14.
