Police and the military aren't attacked in the US because the majority of Americans think those are good things. Americans want white supremacy and classicism enforced. Americans just think the enforcement is being done to the wrong groups, so they carry out mass shootings against schools, churches, etc. as a correction.

The actually oppressed are in no position to openly engage in warfare against the government. MLK pointed out it would be a disaster because the retaliation would exceed any forces black Americans could muster. Look at how much pearl clutching was done in the wake of the George Floyd protests. The so-called moderates immediately supported the pigs throwing people into unmarked vans.