This is the theme from the third level of the platform game Uppercase of Emergency.
In the third level the protagonist finds a city under siege. People that resemble American Indians are attacked by flying robots and the boy uses his magical typewriter to help them. It's pretty much the theme that I'm least satisfied with because I didn't manage to find a good balance concerning the seriousness/epicness. I removed some details to not make it too spectacular and now it seems as if something was missing.