The nature of cultural social relations must be understood. For example, foreigners adapting to the United States should learn that Americans are more likely to form more superficial friendships than is typical in many countries (Stewart, 1972). Immigrants may be bitterly disappointed when they discover that Americans typically do not expect or accept the strong commitments and obligations frequently associated with friendship in other cultures.
From a very interesting study by Arizona State University about cultural shock posted by a friend on his blog.
What do I think of it being in the US for 4 months? True in my case so far, although I never expected to find a country friendlier than Brazil. Not that all friendships are actually deep, but the feeling of being welcome and warmness may be hard to find somewhere else.
One curious thing that I would like to avoid when facing the cultural shock is the "[...] isolation, for example, living in an ethnic enclave and avoiding substantial learning about the new culture, a typical lifetime reaction of many first-generation immigrants."
Whenever I saw other friends abroad, we never know what they go through. Rarely you see them writing or sharing their hard times in the new culture.