First, I think save the world stories are bad gaming. I just don't find them compelling or worthwhile to participate in.

Second, before something like that can have impact, they have to have spent enough time on that planet and with the people there to be fighting for something if you do decide to do that. As an example, my grandpa who had fought in ww2 said it wasn't the country that motivated him. And certainly not other people's countries, but defending people he knew and cared about. Most of the time he was fighting so the guy next to him could go home.