Seasoned travelers recognize that cross-cultural politeness norms vary and respect is manifested through diverse expressions. Thus, members of cultures where communication is more direct are usually perceived as blunt or unrefined by those who have been raised in communities that value the so-called soft skills. Conversely, what is regarded as civil expression may be considered superpolite in societies which value group harmony and avoid direct confrontation.
In Spain, for example, much of the meaning of an oral message is often derived from non-verbal cues, shared understanding and context. Instead of resorting to phrases such as could you possibly...? would you be dear and...? speakers will typically state what they would like and use few softening expressions, if any. In social gatherings interruptions are seen as a sign of engagement, not rudeness. As a matter of fact, silence in a conversation is often understood as a symptom of coldness or hostility and speaking in a roundabout way may feel contrived and suspicious. Indirect language is the type of expression associated to people who are trying to hide something. The sentence there is room for improvement is a way of masking an unpleasant truth. Would you rather hear that or you're not good enoug? How about you can do better?
Roughly speaking, in Spain we prefer honesty to extreme politeness, but there is a downside to our frankness. Oftentimes it makes us look abrupt or impolite to members of cultures in which courtesy is a priority. In reality, it is all a matter of perspective and choice. A tactful opinion uttered with an unsmiling face might defeat its very purpose and a friendly tone can sometimes make up for a slightly harsh statement. I know. Still, you're probably reading this post because you want to know how to be polite in English. Unfortunately, there are several ways of interacting with others in a polite manner and it's your duty to choose wisely.
Just think about this. When a friend wants your opinion about their objectively horrible sweater, what should you do? Lie? (I think it is nice) Tell the truth? (You look silly in that thing). Be sarcastic? (It definitely sets off your eyes). Avoid a real answer? (It's very you). There is no clear-cut response. You may argue that it all depends on individual speakers, that everybody is different, that some people are diplomatic while others don't hold back. And all that is most definitely true. However, not everything depends on individuals. Whether we like it or not, we must accept that certain cultures promote certain modes of expression and if you're learning English you should not dismiss cultural conventions that happen to be prevalent in most English-speaking communities.
Needless to say, there is significant variation among Anglophone people from different cultural backgrounds. That said, I believe some guidelines can be considered without slipping into crude stereotypes.
Generally speaking, Americans tend to be more verbally direct than British people. What do you need? is actually not an unusual question in the U.S. and a statement such as Netflix needs to fix this problem is more likely to be heard in Wisconsin than in Dorset. The funny thing about it is that, in a case such as that, there is no pressing need involved. The speaker is simply voicing a opinion in a way that feels "normal" it their dialect. A British speaker, however, might typically opt for a softer approach: I think they should fix that problem. That second option includes two filters: I think (=it is my opinion) and they should (=it is my advice / they don't really have to do it). Of course, being too courteous can also be problematic. Much like excessive irony, which morphs into sarcasm, politeness can become hypocrisy or involuntary self-parody. Also, is it fair to force your interlocutors to decode your constant euphemisms, understatements and white lies? I would say yes. To a language learner tentative language may be unclear, but to the native speaker most verbal cues are crystal clear even if occasional misunderstandings between American and British speakers do occur from time to time.
Whatever your thoughts might be on the tricky question of politeness, I believe that an advanced English speaker ought to be attuned to the nuances distinguishing a pressing demand from a tactful suggestion. When you're asking for a favor, remember that the sequence I need shows little consideration for the interlocutor and reveals a certain sense of entitlement. You can use it in certain contexts, of course, but it probably shouldn't be your default option if you're telling someone what you would like them to do. Just consider the difference between what you want is... (which is a casual way of giving advice in the U.S.) and if I were you I would.. (which reveals a more tentative approach).
The video below is a tongue-in-cheek explanation of how British manners work. Personally I find it delightful: the actor's tone, his voice, his over-the-top RP pronunciation. Everything is perfect. And even though it's obviously meant to be funny, there is a real message in it.
