The time the war was set in wasnt the problem, the problem was McG not showing what the previous films mentioned.
Just listen to some of the lines from Reese in the first movie:
"You stay down by day, but, at night you can move around, you still have to be careful though as HK's use infra-red"
"The 600 series had rubber skin, we spotted them easy but these are new, they LOOK human"
"Most of us were rounded up, put in camps for orderly disposal."
"....Some of us were kept alive... to work... loading bodies. The disposal units ran night and day. We were that close to going out forever. But there was one man who taught us to fight, to storm the wire of the camps and smash those metal mother****er's to junk, he turned it around, he brought us back from the brink....his name was Connor."
Honestly, how many of these comments actually made it faithfully into the movie?  The time wasnt the problem, if they had showen what Reese described we would have had a superb movie.