A key aspect to civil breakdown is absence of the rule of law, which is a cornerstone of every functioning society. The rule of law may take the form of religious enforcement, as in Saudi Arabia, or, as we know it in Western democracies, through the criminal code enforced by police and the courts.
The US, despite having been free from home-grown Muslim attrocities so far, has many urban areas where rule of law has broken down, and where gangs of thugs run rampant, providing their own means of enforcement. I've seen this happen in my home town, Detroit. I had no fear growing up there in the 50s and 60s, but now I will not enter the city unarmed. I can, however, walk freely in Dearbornistan among the burkas and beards at any hour.
I submit that restoration of rule of law, with the likelihood of arrest, conviction and incarceration restored to a deterrent level, would go a long way toward reducing our local terrorism threats. The burden of proof seems to be held too high on matters of conspiracy, abetting, and incitement, and vicious predators are too often allowed to go free to continue their bloody endeavors.