You have probably noticed a difference in how informally and formally people interact with each other.
Cultures, like the United States, are sometimes called egalitarian, symmetrical, or horizontal, because we believe that humans are created equal. Interpersonal relationships follow this theme of equality. Interpersonal relationships operate on a fairly equal basis regardless of differences in age, sex, status, or rank.
In horizontal cultures, communicators frequently are informal. In North America, people tend to treat others with informality and directness. Often they skip the use of formal codes of conduct, titles, and ritualistic manners in their interactions with others. They may prefer a to be on a first-name basis and expect a direct communication style.
Some cultures are referred to as vertical or complementary, because people are assumed to be unequal or un-egalitarian. Interpersonal relationships take place on hierarchical levels that supply individuals with guidelines concerning how to behave.
In vertical cultures, people believe that formality is essential. The value of formality in verbal and nonverbal styles allows for a smooth and predictable interaction. Both verbal and nonverbal communication styles depend upon the status of the other person.
Overall, the United States is quite informal. Often we use first names sooner than any other culture, even with our supervisors and managers. When it comes to other cultures, pay great attention to the way people introduce themselves, or ask how they would like to be addressed, and you should be just fine.