Seriously, the unrest is brewing in our towns. The powder keg is filled to the brim, all it takes is a spark, and any kind will do, to blow it up. You're getting close to a critical mass of people who are severely unhappy with how things are going, the only thing missing is a focal point for this anger. As soon as a justification is found to vent that anger, you have a riot.
Seriously? Critical Mass? Seriously?
I kinda doubt it...this is pretty isolated. Seems mostly to just be a problem in the few highly packed urban centers in the US. You don't see this type of behavior, or even sympathy to it in most of the US.
And for the most part, I think the 24/7 news channels blow it up to much more than it actually is. They often choose camera angles to try to make it look like more people than it is.
The majority if folks in the US rarely if ever have a personal encounter with the police in their cities. The majority of US citizens while concerned that these isolated events are coming to our attention, they also don't see it as much a problem in their local areas or states.