Lots to unpack here. I'll start by saying I'm fully aware of the Great Leap Forward, and what I meant by a "long time" is the living memory of the majority of Chinese people. I'm 39, which puts me right about the median age in China, and I have no memory of China's economy doing anything but expanding. We just don't know how the people will react if they're left holding the bag. I fear that it will make Tiananmen Square look like a picnic.
Also, my reference to the Balkans was the pre-WWI Balkans, not the post Cold War Balkans. Not that it really matters. The Balkans and the MIddle East are destined for strife for a long time. In the 1910s Balkans, there was a lot of unrest. People wanted to be rid of the Hapsburgs. IIRC, Ferdinand's killing was perpetrated on the anniversary of a famous battle in the 1200s or some shit. I guess it was symbolic when you've had so little self-rule that the 700th anniversary of winning something is still important to you. The Middle East post-Arab Spring and post-Islamic State has left the place even more in ruins than it was. My assumption is that it could easily be the start of a major international incident, paralleling what happened in 1914. Not saying it's likely; just saying it's easily imaginable.
I fully agree with you that a civil war is highly unlikely, and for the reasons you cite. There's no regional specificity to our problems. Even within conservative states you have 40-45% of the population being liberal and vice versa. Urban-rural divide doesn't track so well as a stark geographic divide. I can however easily see some form of domestic terrorism increasing, and not just of the Timothy McVeigh variety. Perhaps maybe we'll see young liberals trying to terrorize the Zuckerbergs of the country. I wouldn't participate but I might also think some people get what they deserve.
And let's face it. Doing exactly what the Republicans did legislatively is bad. Bad. Full stop. It's no way to run a society. You can't fight absolutism with absolutism. Tell people no and they'll say, "fuck you." Show them a better way and they may want in. Infrastructure is a better way. Even Trump thought that. He had infrastructure week like 50 times in 4 years. Don't fuck this up, guys.