It is one of my least favorite things about American culture and I would be thrilled if everyone stopped putting so much emphasis on appearances and started looking inside each other for value.
Although I agree with you fundamentally, my experience is that American (western) culture is actually better than most other cultures. Asian, especially Japan/Korea/China are utterly brutal in terms of criticism*. (I have examples if you are curious about the differences). OTOH, both south asian and south pacific are not like this, as far as I can tell.
It's also true in large parts of Europe, mostly Eastern Europe. Northern Europe differs too much, AFAIK, although I don't have much experience there. What I do hear is that places like Denmark are a lot "darker" and harsher, compared to Finland and Sweden in which there is more personal space around people.
---
I don't think STFU and MYOB works. I wish it did. The problem is that these are social pressures, punishing social defectors, meaning anything outside of the norm is ridiculed.
I believe that the only solution is to use a social rebuke for people who are critical, effectively using the same method. In small groups, a question like "why do you think it is acceptable to criticise others?" can be quite painful. If enough people do that, a new social norm replaces the old.
---
* One odd thing that comes up in Asian cultures is the criticism comes with support to become 'normal', or will easily integrate good and bad traits together. What is fundamentally different in Western (and namely American) culture is the overlying belief that we are fully responsible individuals, and hence something is
wrong with us whenever we defect. That attacks self worth differently than a lot of other more vocally critical cultures.