The class structure of Vedic society was regimented with strict divisions that everyone understood. These divisions became the caste system that defined where people were and what could be done:
At the top of the chaturvarnas were the priests, or Brahmans. Below the priests were the warriors or nobles (Kshatriya), the craftspeople and merchants (Vaishya), and the servants (Shudra), who made up the bulk of society. These economic classes were legitimated by an elaborate religious system and would be eventually subdivided into a huge number of economic sub-classes which we call "castes." Social class by the end of the Rigvedic period became completely inflexible; there was no such thing as social mobility.
This becomes a critical point in understanding the class structure of the Vedic society. Roles were defined, elements were understood, and where people were was what they could do and how they could live. The establishment of these stratifed groupings defined the Vedic class structure.
Certainly, there is a class structure in America today. It is the same structure that ensures that Bill Gates and myself reside in different realms of being. However, there is no institutionalized class system in America. There is nothing prescribed that says specific people occupy specific roles in society. It might very well turn out to be that way through different conditions, but the difference between the Vedic structure and the American social setting of today is the absence of a strict regimentation that defines people from birth. Again, this might be there in American society, but there is nothing institutionalized or codifed suggesting that it is a form of social law as it was during the Vedic period. Whether one sees it as a myth or reality, social mobility does exist in America.