It's unlikely @Quantumcat meant every American was brainwashed. More likely, she was just addressing the very real disease that is American nationalism.
Is that disease showing up now? I haven't seen the things she's claimed in the wake of this particular issue, so it's rather odd to bring that up. Before the massacre? Okay, I can kind of see that, but now? And addressing the gun control response. Just...something! Do something! Congress, Trump, any legislator, just fucking do something! That's all I want, something, not nothing. My body temperature's warming up just typing this out, I'm passionate about that plea. Just do something for fuck's sake.