Shawn of the Deli said:

There is that great scene where Kyle returns to resistance "hide-out". He is exhausted. The humans are, by and large, NOT soldiers. Old people, young people, all of them dirty and sickly and looking like hunted animals. We hear people weeping all around. Then the Terminator shows up and just lays waste to the to the place. The scene is bleak and horrible and drives home how desperate everything is in this future. Terminator: Salvation never gets close to that. Most everyone is a soldier toting around full special forces gear. They have jets and hangars and submarines. Instead of feeling like humans are on the brink of extinction, we get what looks like GI Joe fighting Transformers in the desert.

This kind of makes sense with what we know of the changing timeline from the TV series. Instead of it being a rag tag group of people that are caught up in the mess, it's a bunch of people that have been sending other people back in time for a while, increasing each others knowledge of what's to come and changing things along the way. I don't think the TV show ever outright says it, but it's heavily implied that each time someone else goes back, something in the future ends up different (a new timeline is created). C3PX explained it perfectly and it seems like the movie is going along with that idea.