FWIW, I've encountered several times that German or Russian directness was considered impolite or even offensive in the US, for example when you'd point out that there was a mistake or something not conforming to spec without prefacing it with "Thanks for the awesome work! This is real progress. A minor issue we could still improve might be this:", etc.
So, as you point out, these conventions exist everywhere, and (like the proverbial young fish asking "what's water?"), they're hard to see when you're in the middle of them, and consequently much easier to see when you observe them in a different culture.
So, as you point out, these conventions exist everywhere, and (like the proverbial young fish asking "what's water?"), they're hard to see when you're in the middle of them, and consequently much easier to see when you observe them in a different culture.