Or

Let's make another Terminator movie, send the Terminator back in time and inform Lloyd George and the political aristocracies of Europe that the Treaty of Versailles would lead to the rise of Nazi Germany and so predominate the historical landscape of the 20th century that it is impossible to separate the Cold War from it's ill-effects.

Or

Let's make another Terminator movie, send the Terminator T-1000 back in time and tell that stupid jerk Reagan that he could engage the Soviets in a catastrophic financial contest without actually spending trillions of dollars on nuclear warheads that we are currently spending trillions of dollars dismantling and tracking as they inevitably bleed into the black market.

Or ...and this could already be in production…

Let's make another Terminator movie, send the Terminator back in time and send him to Iraq, where he would kick some serious Al-Qaeda ass, befriend a little Kurdish boy who brings out the human spirit in his Terminator source code, which emerges in time for him to sacrifice his cyborg life in order to kill Osama bin Laden in some FANTASTIC way that has lots of explosions..more explosions than anybody's ever seen on film!!!!

Why not just have the Terminator arrest Osama before 9/11? Or inform the authorities? It's a Jerry Bruckheimer film, for chrissake.