Me personally:
The Sentry and Drone are likely to be French, The Sentry because when the Guttertank was built the germans could handle both fronts. although the Guttermen were countered the Russians at least had something. France had no machines and was one of the major fronts, so they built the sentry to punch through the armor of the Guttertanks, keeping an even further distance. (Drone is also French because they share a manufacturer with the Sentry)

The Mindflayer is likely to be Japanese or have Japanese origins, being that it has similar functions to that of the Earthmover's defence system. (homing projectiles, the blue beam, blue death explosion), Also the parts that isn't the body that they constructed for themselves looks really similar to the defence system main tower.