My point of view , from Europe, is that political violence is already there in the US. As well as state violence (not just on political opponents, but also on all minorities and "people who have a different opinion").
The next step is indeed a second civil war, with 21st century characteristics (hybrid war, etc...)
I am not enthusiastic about the near future for the US nor for the world.
Ironically, if a civil war was going to happen it will be because Trump's overuse of the military. It is such an newbie African dictator mistake. Every time you use the military to put down civil unrest you give them an inch of your power and before you know it, they figure they don't need the regime anymore.
You will never see Putin outsourcing civilian tasks to the military.