How do you recommend drawing attention to systemic issues of national mindset where these issues are so much "in the water" that they seem invisible to insiders, but are quite notable to outsiders?
EDIT> More specifically the US/Canada differences are interesting because as Canadians we are very similar, we are immersed in your media, and your products, and yet your values seem gratingly foreign at times. It's a valuable perspective, IMO.
We don't mean to do that—on the contrary, we think we're helpfully pointing out information that other people need in order to improve themselves (which in most cases means, be more like us). But the other side feels it acutely. We don't see or feel the shadow we cast when arguing like this, but it's the first thing the other picks up on. Then the impulse becomes irresistible to fling it back—which the first person experiences as being misunderstood and unfairly interpreted—and so we get fights where people are no longer exchanging information or learning from each other. I believe that this may be, in the small, the same phenomenon which in the large is known as war.
So my recommendation would be: don't do it. But if you have to do it, hold off until you've conscientiously searched for unhelpful signals in what you've written and unhelpful intentions that may be lurking in your feelings. Take care to give space to the other side and to allow for how your own biases affect your view of the other. (If you want to look into the latter, one place might be with the feeling behind that word "gratingly".) On HN, there's an additional don't-do-it: don't do it if it would take a thread on a generic tangent. Those lead to much lower-quality (high indignation, low information) discussions.
All that is so hard that it's better just to not go there. Instead spend the energy on processing why one feels the need to go there in the first place—especially on the internet, where misunderstanding is on a hair trigger and human bandwidth so painfully low.