Meka is mechanical with the edges sanded off. The genre forked early and the fork is the taxonomy: super robot, Mazinger Z in 1972, piloted like a hero's vehicle, versus real robot, Gundam in 1979, mass-produced like a tank and sold as model kits.
The founding stories are domestic, not military: Tetsujin 28 is a wartime weapon inherited by a boy detective who aims it at better targets, and Astro Boy is literally a grieving professor's attempt to rebuild his dead son. In Japan the robot enters the story as family. In the West it enters as Frankenstein, the creation that comes back for the creator.
The claim: Japan loves robots because Shinto already told it that tools get souls, tsukumogami, the objects that wake as spirits after a hundred years of service. The mecha is a kami with a cockpit, and Western robot terror is just what a culture feels when it never believed its things were alive.
Why does one culture dream of robots as children and another dream of them as uprisings?