One of the difficulties faced by students learning to read English are the cultural assumptions underlying the language. To a native speaker, these are like breathing or walking; we don't need to think about them because they're so familiar, we automatically know without even realizing. For example, in English we differentiate between genders. A student from a culture where gender isn't recognized in the language will often find it difficult to naturally distinguish between “he” and “she” when speaking or writing (and by extension, when reading; they may notice the words but not consciously or subconsciously grasp the significance). This may seem unimportant at first, but not recognizing the gender markers could result in a student reading something about a woman, perhaps a behaviour or a decision she has made, without understanding its context.
In another example, students who are more familiar with rote learning styles may have difficulty comprehending argumentative language. Since they have been taught to believe that the information they are being given is correct and that the teacher is a final authority, there is no reason why a teacher (or the essay they're reading) should be required to prove its point of view, much less provide supporting evidence. If the information is correct and absolute, then argumentative language isn't necessary, is it?
This is why understanding Western culture is such an important part of learning English (and by extension any language). It becomes even more important when preparing for a reading exam or test. Now, on top of having to understand the complexities of English which run deeper than grammar and vocabulary, the student must conquer them with the added pressure of a time limit. Suddenly, reading English has more in common with defusing a time bomb than enjoying the company of an English speaking friend.
To make matters worse, the student has been challenged to not only master grammar and vocabulary, but also to know and understand the history of Western Civilization. Gee, no pressure there. There is, however, a much simpler solution.
In learning to understand Western culture and apply it to learning English, a student could focus on being aware of the differences between Western culture and their own culture. Students who are aware that English has gender markers and their own language doesn't will find it easier to catch their speaking mistakes (struggling with when to say “he” or “she”). They will also find understanding argumentative language less difficult. It won't become easy overnight but at least they will have a fighting chance. With practice, understand English's complexities will become easier over time.