I don't think anyone can say that with any assurance
Look to the middle east for lessons on urban guerrilla warfare.
How effective are the Muslims against Israel? The Palestinians have support, they have supplies, they have people willing to die for their cause, yet after 70 years they have nothing to show for all the deaths.
But you've cherry picked only one of the 10 or so Civil Wars going on in the Middle East.
Israel is a pretty unique place: a de-jure ethnostate with a highly motivated first-world and high-tech citizen military supported by the worlds top superpower VS. largely impoverished and corralled opposition.
Consider a few other Civil Wars ongoing in the Middle East and it's not so clear that they always fail:
Paid rioters catching random individuals or facing police under orders not to react with too much force is not a civil war. It is riots.
Sure, no thoughtful person would claim it is. So there is little risk of 'antifa' riots escalating into a civil war, I agree.
Vicious inter-tribal sectarian conflict is real, in fact it's the norm in the world. In places where the most common tools are farm implements like machetes they are fought with them. In America guns are far more prevalent then machetes, so if the will to fight is there, it will look a lot like a typical un-conventional war.
Our nation has seen riots before and will see them again.
Again true. But we've also seen Civil War before. And taking a expansive view the War Between the States wasn't the only one. The Mexican-American war, the Indian Wars, the war of 1812 - all had strong elements of Civil War in them.
I suspect most of the demonstrators in these leftist riots are just young people enjoying themselves destroying property. If they thought there was a possibility of them dying during the riots they would not participate.
Right. If you look at the list of books that speculate about a future CWII scenario none of them begin with Toy Leftists as the progenitors of the war.
If you want to believe that the United States of 2018 is similar to all the other conflicts and if you believe that there is a possibility that there will be an armed insurrection.... then okay. Believe what you want.
Time will eventually reveal which view is correct.