First off it's not civil war. It's a handful of tyrants versus millions of people. If things get violent it would be a revolt. Second if you're thinking about factors like corrupt police, it's still an ants versus grasshoppers scenario. Third if all communication infrastructure goes down or something along those lines, you'll be up against whatever enemy is in your city's streets. Who would that be, that would actually be scary? Only realistic answer is the military. If the majority of our military seriously starts fighting citizens then it's the end times and I'll be having some fine wine and prayer.