Die Mannschaft secured a 1-0 win in Recife on Thursday through Thomas Muller's solitary strike, progressing through Group G as winners as a result.
Despite the relatively slight margin between themselves and the Americans, Lahm the victory represents a development on the 2-2 draw with Ghana and show that Germany are heading in the right direction.
"We made big step forward," the 30-year-old told reporters.
"We did better than against Ghana. We can be absolutely satisfied.
"That's what makes our team strong; that we are very defensive, that everyone defends. That is what's important in a tournament like this. I had the feeling that the team really works together - in the defence as well in the attack, and that's a good feeling."
Lahm also reserved special praise for his Bayern Munich team-mates Bastian Schweinsteiger and Thomas Muller, singling out their contributions to the team.
"Thomas Muller is an excellent player," the DFB-Elf captain added.
"He is very important for the team. He is a threat in front of goal, because he anticipates what happens in the box.
"Schweinsteiger has always been an important player for the national team. He is a big personality and therefore important for our game and our team.
"Of course, I notice the discussions about myself," he continued when asked about his own performance.
"I don't live in a vacuum. It is important the team develops constantly."