Breaking down this scene, you can see how each shot uses screen direction to help tell the story. The Americans run and shoot left-to-right, while the Germans shoot right-to-left. In shot 5, there is no way to really know which side those two guys are on.

The only clue is they shoot L-R, so we assume they are Americans. If we flipped the shot so they were shooting R-L, viewers would assume they are Germans.