More importantly, is making an 8 year old kid a km by themselves in rural America a significant risk ?

I feel like I would have done this 1000 times by the time i was 8 in the rural Australia, is the danger in the US that much larger ?

My guess is that the mother was removed from the child not as a punishment to her, but in order to ensure the safety of the child. In other words, deterrence rather than retributive justice. FWIW, I do agree that this is a huge overreach on the part of the police and that "situational awareness, perspective, nuance and understanding are completely missing."