Here's the thing about civil wars. There is a recipe that is true in almost every case:
Two or more factions within the nation hate each other's guts. This can be for religious reasons, social reasons, or economic reasons.
The two sides vy for political power at the highest levels, and upon getting hold of it, use it as a weapon against their hated rivals. This becomes tit-for-tat after so many years, where government decisions are made almost as much on the basis of "fuck those guys" as they are on beneficial policy. [YOU ARE HERE]
Civil wars are almost always started by the government, and almost always by accident. Some event happens that captures the nation's imagination, and the government reacts in a way that provokes VERY widespread resentment among the faction that isn't in power. This leads to…
The government has fucked up. They are playing obvious favorites to their faction of the people and the rival faction is mad as hell and not going to take it anymore. They take to the streets, protest and riot. Note that this requires a specific event, not just general butthurt rioting like we've seen. The rioting goes on until…..
This is where shit gets real in earnest. The government gets fed up with the rioters and drops the hammer, specifically using excessive and/or extralegal force. Maybe a bunch of protestors get shot, or a no-knock raid kills the rival faction bigwig and gets labelled "assassination." Whatever form it takes, its massive and overbearing. This leads to:
For a civil war to happen, a certain percentage of the population has to be ready for it. The breakdown goes like this: At least 13% of the total national population have to be willing to explicitly support an armed civil conflict. Of that 13%, at least 3% have to be networked, armed, stockpiled, in communication with eachother, possess detailed plans, and ready to actually carry out organized armed violence. The remaining 10% will be where the funding donations, safe harbors, alternative media, and general material support for the rebellion comes from. If the nation in question passes this check (and I believe the US does), then we move on to the last phase. If it doesn't pass the check, you end up with a "Days of Rage" or Northern Ireland "Troubles" scenario of low-level terrorism and political crackdowns for X number of years until it eventually peters out.
Suddenly the government crackdown meets a hail of gunfire and grenades coming from the side of the protestors. Reprisal attacks by organized groups start happening, targeting government and power-faction leaders. The police intervene and shootouts start happening. Bombs go off, buildings get blown up. The government resorts to military force to try and contain it, so the rebel faction appeals for international aid from sympathetic countries and organizations like drug cartels and foreign enemies of the US. Both sides fight to sway the opinions of the public - MSM under the government, rebel media under the other faction. The rebel faction appeals to the military for defectors, weapons, and supplies. If the population is truly ready, some percentage of the military defects, taking their gear with them. Now the rebels have AT-4s and .50cal machineguns. The fighting intensifies as neither side gives ground. The economy goes tits up due to the instability and blown-up infrastructure, and suddenly millions of people are out of work, ripe to join one side or the other to fill their belly. The more heavy-handed the government gets and the more civilian casualties there are, the more pissed-off people join the rebellion.
In the end, it'll be decided by the military itself. They can choose to let the rebellion take over the government, or enough territory that the government finally gives in and negotiates. Or they can go all out against the rebellion and try to crush it, wrecking the whole country but likely winning. Or they can do neither, follow orders, and try to keep chaos to a minimum, which means the conflict will never truly end and you get the "Godzilla walking through your neighborhood weekly" scenario that one guy described.
