The WWII Japanese militarist state was a particularly intense concentration of suck, yes.
OTOH, the USA has been at it for longer and on a much larger scale.
Soldiers in action will commit war crimes; this is pretty much inevitable. Young men, trained to celebrate violence, placed under extreme stress, facing people who they are encouraged to dehumanise (and who are often racially and culturally distant from them), will predictably do horrific things. Not all of them, but some of them.
You can reduce the incidence of war crimes by (a) stomping the perpetrators hard when they occur, and (b) not deploying military force unless there is no other option. The fact that atrocities are an apparently inevitable part of war needs to be part of the calculation when evaluating the cost of military action.
The US is a notable failure at (a) as well as (b), and has been throughout its history. Hence, the US military commits an unusually large number of war crimes.
