Failing to say it will be both surprising and worthy of criticism. Not knowing the norms of another community is the (c)central problem of cross-cultural communication. To continue the Thank you example, even though another culture may have an expression that appears translatable (many don’t), there may be (d)similar norms for its usage, for example, such that you should say Thank you only when the cost someone has caused is considerable. In such a case it would sound ridiculous