Americans are very uncritically accepting of their system of government in general. It gets taught as this "wow, our system of checks and balances, isn't it amazing!?" and by and large is never criticized or substantially analyzed as to whether it's a system that produces good outcomes. It simply is.

The largest criticism imo is that it biases against action. Every dimensionality of the population gets represented (popular, geographic, regional, etc) and if any segment of the population disagrees, the whole process can be dragged to a halt. And as the Polish Sejm showed hundreds of years ago... the liberum veto is a terrible idea politically. And everyone knows that, but, what is the threshold at which it becomes a bad idea? 90% consensus? 70%? Pure majority? The US system requires very high consensus as some issues show - there are some issues with >90% popular support that still cannot get passed.

https://en.wikipedia.org/wiki/Liberum_veto

Consensus building is good but at the same time there always needs to be someone in the drivers' seat, the idea of "split government" in the sense of the executive and legislature being opposed is fundamentally and innately a bad idea that people just uncritically accept because that's how it is. Again, the executive being the leader of the coalition that controls the legislature is a good way to do that - and then we can work on making the legislature represent the population fairly in the desired ways.

Most of the problems with the US really boil down to "bias against action" and "split government" and "the senate in its entire conception". And federalism really is not great when taken to the degree that the US takes it, either, but again that's something where it's taught as "wow, federalism, how great!" and its downsides are never mentioned. Having regions of the country where human rights are 100 years in the past is pretty bad. Gay marriage wasn't constitutionally protected until like 10 years ago, and it was by court decree, not actual constitutional process. Texas just goes around killing people, some absurd % of the executions happen there and the evidentiary bar is quite low. Social services tend to be similarly scant in these regions and again, it’s not a good thing that states can just choose not to fund (or to place arbitrary restrictions on) senior care or other funding for vulnerable populations. Federalism is supposed to be backstopped by a minimum bar that in practice doesn’t exist in the states, in human rights or social services or many other areas.

Unfortunately, a lot of this was historically necessary to get the US built - you wouldn't have gotten the slave states onboard if they didn't have disproportionate representation and mechanisms for dragging abolitionism to a halt. And it's produced one civil war and a half-dozen-odd constitutional crises over the centuries. But that part gets separated away from the “design choices”, and people only hear the positive.

It's not that they're all inherently bad either but they're deliberate design-decisions that have consequences both positive and negative, they are "tech debt" from politicians who wanted to move quickly and break things, and now they're these sacred cows. And in hindsight some of those design-decisions have been ones that had immensely negative consequences and can't be easily undone... but they were necessary at the time.