The US will become an authoritarian police state when it starts silencing all opposition to the state as a matter of course. That isn't the case yet. However, the processes, institutions and technology available to the US government already seem quite capable of facilitating authoritarian control. Personally, I suspect that it's just a matter of time. All the things you talk about have happened, but they happen rarely. With the right leadership in power, they could easily start to become commonplace. The thing is, anyone who says something that doesn't conform to state ideology can be said to be aiding terrorists, by spreading an "extremist" message and implicitly encouraging others towards terrorism. The general public seem quite happy with whatever treatment "terrorists" get, so I can't see there being much standing in the way.