Sure, so the question I was responding to was, why not carve up states with multiple metro areas into multiple states? Why not have e.g. North and South California, if we're going to have e.g. North and South Dakota?

The reason this is a difficult question is that, while the US is a federation of states, there's no real guidance on what a state should be. The idea of "one person, one vote" is pretty clear. We can debate what the voting age should be, whether non-citizens should vote / what type of residence status you should have, whether your right to vote can be rescinded as a criminal punishment, etc., but we're starting from a common framework. Even in cases where we know that certain sub-populations have higher birth rates than others, there's no serious proposal to try to "correct" for that effect, because it's not seen as incorrect.

The principle of "one state, one vote" has no corresponding mental model for us to follow. If the US had no states, and someone said "States are a good idea," how would you draw the boundaries? Why would you draw a line across the Dakotas but not across California? Why would you separate Wyoming and Colorado? Why would Manhattan and Long Island be assigned to New York?

(Note that residents of a state have very limited ability to have opinions about their state boundaries - new states require "the Consent of the Legislatures of the States concerned as well as of the Congress." Concretely, if Californian voters wanted to split North and South California, but senators from other states said no because it would change the balance of power in the Senate, it wouldn't happen.)

And again - what is special about rural voters and only rural voters that they need this system? Why not give renters an extra veto, or the working class, or people in service industries, or racial minorities, or religious minorities, or field-of-employment minorities, or whomever? You can do this straightforwardly by having a Senate with either elected or appointed members from specific constituencies.

Hong Kong, for instance, elects half its legislators from "geographical constituencies" and the other half from "functional constituencies": https://en.wikipedia.org/wiki/Functional_constituency_(Hong_... These are generally industries, but one of them is specifically a representative of rural interests.

Because of specific sectarian conflicts, Lebanon's legislature is divided equally between Christians and Muslims: https://en.wikipedia.org/wiki/Parliament_of_Lebanon#Allocati... And they have a concrete reason to want this (it was negotiated as part of a peace settlement after a 15-year civil war). I don't think the US has anywhere near as strong of a reason to privilege rural voters.

Also - the current system doesn't even privilege rural voters. It privileges rural voters in states without significant numbers of urban voters. There are tons of rural voters in states like New York and California who do not get to control their state government because major cities are more populous. California is even the biggest agricultural exporter among the states, so it's hard to say that the current system actually does give rural voters extra veto authority.

All it does is what you said - it gives less populous states extra veto authority. This is the same axis as "one person, one vote," just in the opposite direction. So what's the reason for it?