I mean I have an answer which helps me understand but it is not a particularly “satisfying” answer… the answer basically boils down to this being a mathematical

I mean I have an answer which helps me understand but it is not a particularly “satisfying” answer… the answer basically boils down to this being a mathematical theorem. So you have an election cycle. Each election is a function Polity → Polity, the people who performed the election look at the election issues and they vote and they look at the results and they are changed by that process. A cycle of these will chain a bunch of these together; the time delay between them is a sort of diffusion process in the middle of them. That diffusion is kind of the only way to escape the basic theorem. So there’s a broad set of theorems about these x → x functions called fixed point theorems; under very general conditions repeating one indefinitely causes it to converge to some value which is equal to its input, x = f(x). So the mathematical theorem says that whatever your election process is, your nation will fall into a state where those elections do not change the polity much, except to eliminate any diffusion. It seems then that the fixed point of the “divide the country into seats and run first-past-the-post elections on each seat” looks like this: 1. There are two spineless political parties. By spineless, I mean that they are not actually associated with real deep-held convictions; over long time-scales you will see seismic shifts, such as a “party of Lincoln, freed the slaves” becoming a “definitely favored by white supremacists” shift or so. 2. Each party maintains approximately 50% of the popular vote, and probably 50% of the control of the government. Note that this happens both with gerrymandering (the House) and without (the Senate). 3. Typical people do not belong to one party or the other. People think they are relatively independent and they disagree with “their” parties in many many ways. What makes that party “theirs” is not their identification with that cause, but their abject terror at the policies of the opposite party. Presumably these three trends continue to polarize the nation until an inevitable civil war. One can also predict that, since the casus belli of the civil war was chosen by spineless political parties, after the situation is resolved one way or the other there will be some sort of movement from the losers to forget that casus belli and recast their motives into new lights as the political climate changes—so in a post-slavery America the US Civil War is understood as not being about “slavery” but about “states’ rights to self-determination,” which is not really about white-washing history (the Republicans after all won the US Civil War and would not mind reminding people of it if that were politically expedient) so much as re-stoking the same demonization of the Other that keeps the system going (“those Democrats are part of a dangerous Northerner lineage that dates back to the Civil War and wants to take away all of your rights in the name of improving your life, whereas we in the South prize individual liberties and would never do such barbaric things”).