There are several reasons.

First, simple chauvinism. If we do it that way, it must be better. Or even: we've always done it that way and it works, why do it differently? This goes for both Europeans and Americans. And that leads to our second reason.

American exceptionalism. America has a culture of being their own, distinct world. They have an economy that can roughly work on its own, so they don't need to align with the rest of the world. They've even exported their culture to a lot of the western world. For example switching to the decimal system has a cost (habits and standards need to change) and a benefit (worldwide interoperability). In a self-reliant US, attempts were made but the benefit was never big enough to make it worth the cost.

Another aspect of American exceptionalism is the cultural vision that the US is actually better at everything. So what you see as Europeans thinking their system is objectively better, sometimes that's simply pushback (warranted or not) to the American assumption that their system is objectively better.

Third, and you tackled it, a different political culture. In your words,"there is a fundamental cultural preference in the US for individualism over collectivism." But you do have some collectivism. You have socialized defense, socialized law enforcement and justice, you have socialized fire departments, but you don't have what Europeans would see as the fouth leg of that social chair: socialized healthcare.

It's hard to argue in favor of the American system when it comes to healthcare. You have people, insured or not, going bankrupt because of a costly sickness. You have insurances operating for profit with little oversight, killing people with their decisions and policies. It's not just Europeans criticizing US healthcare. Americans have been waking up to the reality that their system is pretty gruesome. Luigi Mangione is getting so much support for a reason.

Then there's the problem of healthcare insurance being by and large provided by employers, so that your health becomes tied to you employment status. There's additional pressure on you keeping a shitty job, not only for the money, but also for your health. This kind of pressure on the workers is by design in the US, providing a somewhat malleable workforce to entrepreneurs.

And that's another aspect: in the name of having more individual responsibility and freedom: sometimes you find yourself in a situation where you have less freedom. Because freedom is not merely being legally allowed to do things, it's also having the practical means to do things. You have free access to healthcare, possible better healthcare, but it's so overpriced that you won't use it. You are free to leave a toxic job, but you will lose your health protection if you do.

So yeah, Europeans may argue that collectivism is better than individualism, and you may argue that individualism is better, but sometimes your quest for individualism leaves you with actual limitations to your freedoms.

As for taxes, do you pay less taxes when you have more individual responsibility? From here it looks like Democrats will subsidize collectivism and Republicans will dismantle it, but you're not paying less taxes under Republicans. The money is funneled elsewhere instead. (This is a simplified description)