there were more scenes of the National Guard, but tehy got cut. you can see that in the trailers and also what some guys from the NYNG said regarding how Joss allowed them to act for the camera as though they were really fighting aliens (IE he told them what the aliens were doing, they used real life tactics to react and he filmed it instead of BS Hollywood tactics)
People have been shitting on Bay's Transformers films, but one thing I loved was how he incorporated the military into the film. It made sense on a plot level, but he also knew that the military would know best how to fight alien robots than a scriptwriter would. The Skorponok scene is a perfect example of real military tactics.
I was excited during the last twenty minutes of Transformers, when the battle took to the streets, and came close to feeling that level of excitement in the last half hour of the Avengers. Avengers probably won't age well, but it did feel like a living comic book.