> The bicameral requirement for a concurrent majority is entirely by design and has plenty of supporters. It's pretty egregious to cite this first on the list of supposedly crucial flaws.
The issue isn't the bifurcation of congress by itself, it's that in addition the electoral system for both sides differs so greatly, and simultaneously that the US uses a winner take-all approach to assigning seats which converges to partisanship. Fix any one of those issues and the deadlock issue is reduced. It's the current bicameral nature that the problem, not the abstract notion. However, I also think that bicameralism is oversold - sure, made a lot of sense to try that, but the protections it supposedly provides are extremely slim in a partisan electorate. Part of the time there's deadlock, part of the time it's close (best case, but very rare and growing ever more rare as more congressmen toe the party line), and part of the time there's a trifecta, and there is in essence no bicameral congress, nor even really a separation of powers. The whole thing makes sense only if political parties either don't exist, or are constantly in some kind of coalition. But as in the US? There are only downsides, and virtually no upsides to a bicameral congress. Also, we know more now; other democracies don't have such strongly independant arms and if anything appear more stable.
> The one fixes the other, but adding new states turns out not to be that easy. From a political standpoint, larger states have an outsize cultural and regulatory influence (which is known to the state of California to cause cancer, but which cannot be mentioned in textbooks used in Texas schools) so compensating smaller states makes sense; voters in large states who feel their votes are diluted should, in principle, be able to correct this with a split. Is it a perfect balance? Not at all, but it's something.
Personally: I don't believe this problem is anything near as bad as the current problem (and it's likely overstated anyhow; even large states aren't that large). But yeah, splitting large states would be a good idea, even with proportional representation. But even if there it's worth boosting small states' influence, the current system is excessive. Fundamentally, I'm a little skeptical than non-proportionality is ever a great way to redress that sort of imbalance, but we could easily have a compromise system, e.g. N+1 senators (a kind of smoothing that boosts smaller states). Another thing we could do is limit large states' influence, e.g. by banning stuff like winner-takes-all solutions to the electoral college.
>> that elections at all are in no way shape or form necessarily fair
> A cultural and political flaw, not a Constitutional flaw. Maybe an omission, but you can't write all of the laws and practices necessary for a fair election into the Constitution; it would take up most of the document!
On the one hand: fair enough. On the other: that something so fundamental to a form of government isn't specified is a problem. This isn't black and white; the constitution doesn't and shouldn't include "all of the laws and practices". But the almost complete lack of ground rules - while very federal in spirit - also means that it's a race to the bottom, and what makes sense locally (gerrymandering, winner takes all, etc) isn't good for the whole. The ground rules here are lacking, and that makes sense historically - but then again, that's exacty my point: the constitution is a product of its time, and not a good fit today.
>> that the constitution isn't sufficiently amendable
> A risk-averse and historically motivated bias; we had one bad Amendment (the 18th) and the fallout really put a damper on amendment movements.
It's not just cultural, it's part of the rules too - it's way too easy for a tiny number of voters to essentially veto a change. Also, again, look around the rest of the world (here britain really stands out) - those protections don't seem to help in practice. Britain has no protections whatsoever on constitutional change, yet it hasn't collapsed after centuries. Again, I think that intuitively the idea of setting a high bar for amendments makes sense, but empyrically it does not appear to be borne out. Other protections might be to instead of raising a high bar, create a huge drag - make the process take a long time, and thus require multiple congresses to approve. Have veto-like capabilities, but ones that delay yet further, not prevent reform wholesale.
>> the lack of a checks on the presidency (clearly not intentional, but impeachment is a purely hypothetical check)
> Trump's impeachment trial was heavily impacted by the Democrats' primary season and not-so-subtle party establishment hopes that Warren would somehow pull out a win, so everything had to be rushed in order to avoid distracting her (and she lost badly anyway).
I think you're really focusing on the details here. Set aside whatever political agreements or disagreements you have; the fact is that today's impeachment is a political process that requires going against the grain of partisanship. It's way to attractive to reject impeachment for partisan reasons; because after all - a flawed president one agrees with is still better than giving the other side a win, and it gets worse given the senate's extremely unproportional nature. This causes real problems too; it's not just a question of who wins or who loses - what you see in other countries that have an easier time ejecting leaders is that they try to mitigate damage a lot early, and are a lot more careful to avoid the kind of transgressions that have plagued quite a few US presidents in living memory. And when they do engage in dubious behavior they often seek approval by others at least in their own congressional majorities beforehand, because they know they risk getting hung out to dry otherwise - and that itself is a valuable check on excesses. Alternatively, impeachment itself should have much more teeth.
Maybe trump is too recent a memory, but consider Clinton's impeachment. Sure, I think most people agree questioning a president about his sex life under oath was not reasonable - but lying under oath, really? The only reason that was OK was because the whole thing had the whiff of partisan witch-hunt, and that's a problem, because it'll always be spun to that. I'd rather have a system where everybody knows that if you pull a stunt like that you're liable to get removed. I don't mind if some other leader from the same party takes their place - in fact, that's a good idea, because it makes the process less about partisan rejection of the other side's election win, and more about personal responsibility - but leaders should not be even close to above the law; and right now they are - how bad does behavior need to get before they're actually punished?