The existence of class differences is more present than most people care to think. Rent the movie Gattaca which presents a stratified, class driven, Western society in its full expression. Then decide how much like that society are we today?
Classes exist in human society, always have always will.. but to promote the idea that western society is a hard core caste system if highly foolish. Go visit some of those asian countries where caste systems permiate their social and political structure then come back an try to alledge the US is in the same ballpark... I got news for you its not. And the concept that everyone can be forced to be equal such as communism are complete and utter failures and led to more elitism/peasantry than the feudal systems of the middle ages.
The fact remains, that in the US individuals are free to move through the classes upward or downward based on their personal desire and hard work (for the most part). I know people personally who are very wealthy but intellectually not even close to smart... but worked damned hard and earned everything they have gotten. I also know limosine liberals who have never worked a hard day in their life and live off their mommy and daddies, and I know people who have gone the other way from great wealth to great modesty.
Will most people in the US born to poverty become super wealthy? No. Will most people born to wealth end in poverty? No. But that does not mean that the paths are not open to it, and that people do not or can not do it, in fact the US is truly the most open society on the planet when it comes to an individuals socioeconomic destiny. In a true caste society such movements are impossible, no matter how much talent or ability or hard work those on the lower end have or exercise they never can improve their lot in life.