The US Military, though chain of command, and responsiveness to chain of command, are critical concepts, is unique. It, for instance, trains its servicemen regarding lawful/unlawful orders. In most militaries, there isn't such thing as an unlawful order.
They also train regarding a concept of "need to know". In battle, speed is critical. Sometimes we soldiers need to shut up and execute. Asking why when it isn't mission critical for us soldiers to know "why" can cost the effort in many ways.
But, to say that American troop are somehow "automatons", non thinkers, is very inaccurate. Quite the contrary, we are trained to adapt, reassembe, quickly reestablish chain of command, operate as independent units when necessary, etc.