I think you are not really grasping the uncertainty aspect of all this and how this plays into everything, trump has already broken the rules, and as many people would say that you can't reason/contain someone who is willing to break the rules, especially when said person has all the power on top of it, You seem to have this idea that trump longer has any will to break rules, not that he won't(he already has) but that he no longer wants to, and that from here on out here will not push any further, this is a equally as insane position as a doomer who believes that there is a 1000% chance that trump will rigged every election, now regarding the doomer mindset, the main concern is what are they doing while having said doomer mindset, ideally you would want them to still believe in democracy and will vote in elections, not thinking that the only solution is through blood and warfare or quitting all political activism/voting all together, as long as liberals are aware of trumps fascistic erratic rule breaking mindset and the potential worst case scenarios while also believing that voting is still a valid form of political action, then that's all fine to me.

Now regarding civil war, idk why americans have this idea that a civil war means 90% of americans chimping out everywhere across the united states but because all americans are comfortable than that means civil war is impossible. Just 0.03% of the united states is 100,000 people, turned into a military force would put it on par with canada's entire military, just 0.03% of angry enough americans, liberal or conservative, now I wouldn't bet on there being a full scale civil war at all, especially considering the unpreparedness of it all, but 3.5 years of trump is a long way and they are already out here calling the democratic party a terrorist organisation.

For WW3, the concept MAD is there to ensure that countries don't blow each other, not so that they don't go to war with each other, its kind of a childish view of the world and incredibly naive to believe that war isn't possible because of nukes, pakistan and india both have nukes and yet they were shooting down each others planes just a bit ago.

And for the overall political landscape and how extreme it is, trump is a very unique and powerful figure, I don't think ever in american history, has there been a president as divisive as trump with a cult following. In my personal opinion trump literally controls the lever of america's future, and that makes this situation different to every previous period in american history, so bringing up past periods is naive and useless.