I think in a way there is a cultural failing. This feels like a problem some countries don't have. It's not uniquely US, but how big of a problem are large donors in the Netherlands, New Zealand, or Denmark?
1. Being one of the first lintel democracies implemented, it got some things wrong. The electoral collage and that there’s a local optima in a two party system are the first two problems that come to mind and were avoided by many western democracies.
2. The US is really large - both in population and economy. The large population makes it hard to get enough consensus to make fundamental structural improvements (constitutional amendments), and it reduces the influence of an individual vote for any national office. The large economy means that a special interest can reap large economic rewards by steering policy in their favor, so they try really hard.
> electoral collage
I'd disagree that the US got this wrong; it made a lot of sense historically. These days it arguably introduces some unnecessary inefficiency into the process but I don't think that really matters in practice. The primary objection seems to be that it doesn't reflect the popular vote, but that's entirely by design and arguably the right thing to do.
> two party system
I agree with this but want to clarify that it's specifically first past the post due to winner takes all voting that causes this. It badly needs to be fixed but why would party politicians directly vote against their own career interests like that?
Separately, political parties themselves were argued against when the country was founded but sadly they were allowed. I'd note that most (all?) western countries also got this part wrong (IMO).
> The large population makes it hard to get enough consensus to make fundamental structural improvements
This is intentional. AFAIU, the US political system was specifically designed to be resistant to change in order to avoid the failures of previous republics.
> reduces the influence of an individual vote for any national office
Things were hypothetically (AFAIU) supposed to be done at the state level (think EU) but the interstate commerce clause ended up doing wonders for that.
But something being a compromise doesn't mean that it was sensible - only that it was the best they could do. Furthermore, that particular compromise was hammered out by a very different group of states, and in the context of a very different distribution of powers between the federal and the state governments. Today, we have a much more powerful federal government, we have no slavers to appease, and we have so many small states that, taken together, they can amend the Constitution (via convention) while representing less than 1/4 of the country's population. In this situation, EC becomes a tyranny of the minority, and the majority is not going to tolerate that forever.
You said it yourself. Smaller states can amend the constitution while representing a minority of the population. (I didn't do the math on that but it sounds about right.) So why would they ever agree to directly proportional representation? It's not in their best interests!
Even today, proportional representation is bound to dissatisfy the less populous states whose interests would end up dwarfed by the majority of the population. Meanwhile the more populous states would hardly take well to a fixed number of votes per state. Applying one method to the house and the other to the senate makes perfect sense since bills have to pass both. The problem is that it's not clear how to apply such an arrangement to an election (the obvious schemes would be far too cumbersome). The electoral college seems like a reasonable compromise to me.
(Of course the house is no longer adjusted IIRC, so it's not really proportional representation either. Arguably the states should wield far more power and the feds far less - that would shift attention much closer to home for the majority of issues.)
The Founders warned about this, by the way. This particular bit from the Federalist Papers (#22) was explaining why keeping the Articles of Confederation as they were was no longer tenable. But it's equally applicable to the Senate and EC as they exist today.
"Every idea of proportion and every rule of fair representation conspire to condemn a principle, which gives to Rhode Island an equal weight in the scale of power with Massachusetts, or Connecticut, or New York; and to Deleware an equal voice in the national deliberations with Pennsylvania, or Virginia, or North Carolina. Its operation contradicts the fundamental maxim of republican government, which requires that the sense of the majority should prevail. Sophistry may reply, that sovereigns are equal, and that a majority of the votes of the States will be a majority of confederated America. But this kind of logical legerdemain will never counteract the plain suggestions of justice and common-sense. It may happen that this majority of States is a small minority of the people of America; and two thirds of the people of America could not long be persuaded, upon the credit of artificial distinctions and syllogistic subtleties, to submit their interests to the management and disposal of one third. The larger States would after a while revolt from the idea of receiving the law from the smaller. To acquiesce in such a privation of their due importance in the political scale, would be not merely to be insensible to the love of power, but even to sacrifice the desire of equality. It is neither rational to expect the first, nor just to require the last. The smaller States, considering how peculiarly their safety and welfare depend on union, ought readily to renounce a pretension which, if not relinquished, would prove fatal to its duration."
As a matter of principle government should be as local as possible so as to minimize such concerns. Even without bringing population size into it, it doesn't seem reasonable to be subject to the whims of others across such vast distances. Too much is done at the federal level; states such as California, Texas, and Alaska are already far too large from a governance perspective.
> The smaller States, considering how peculiarly their safety and welfare depend on union, ought readily to renounce a pretension which, if not relinquished, would prove fatal to its duration.
This is the one line of argument that I do buy, but I think it will always be a fairly subjective balancing act at the federal level.
Honestly I strongly suspect that eliminating the interstate commerce clause and outright banning simple plurality voting schemes in political contexts at all levels would resolve most of the currently perceived political dysfunctions.
That it was appropriated to justify the massive expansion of federal power is another matter, but, well... given how absurd Wickard was, I'm pretty sure that if it weren't the Commerce Clause, it would have been something else.
As for majority voting, all alternatives are strictly worse. The problem, rather, is that there's no meaningful democracy at federal or even state level, because there's no meaningful representation at that scale - the "representatives" are anything but. I'm not sure there's such a thing at any scale, actually - for all the purported benefits of representative democracy wrt preventing mob rule, history has plenty of counter-examples, including US here and now (it's a minority mob rule, which is even worse).
I'd rather have direct democracy, but only so long as it's truly deliberative (i.e. not just people voting on a list of yes/no questions put in front of them, like referendums - think more along the lines of, say, how the Constitutional Convention worked). And scaling that requires some form of council democracy, with enough levels that meaningful deliberation remains possible on every one of them, all the way to the top.
By comparison, California has ~40 million people and would be the 9th largest economy in the world if it was an independent country. Ohio has around 11 million people, and the Greater New York City area has ~20 million people.
Aside from structural / legal differences in the US, there are just massive differences in scaling and wealth in the US vs. those countries. They don't have these problems because they just don't have that kind of money and population base.