What do you think is the difference between the Indian subcontinent and the civilizations of Sumer, Akkad, and so many others that shared essentially the same social divisions?
The difference is that the priestly class chose to enclose itself and practice endogamy.And in the other classes it became prevalent as a derivation.
the further the classes were to the priestly class – the looser , the rules governing their conduct.
If one looks at DNA studies the Indian society showed robust miscegenation till about a millenium or more before CE.
And then the genetic picture shows a strictly endogamous trait.
All the stories ,the practices that lionized Sati and Widowhood and Chastity were means to ensure that Endogamy was practiced in a class were Exogamy is still very much a norm. It is even today punishable with death if one married within a Clan or community or village. https://en.wikipedia.org/wiki/Manoj%E2%80%93Babli_honour_killing_case
So why did the classes opt for endogamy? Could it be competition ? Too many of the priestly kind loafing around ,waiting for temples to be built inorder to discharge their duties?
increase immigration? Or the desire to be a part of an organised social order?
But when some Classes close their doors to others. There are those who were automatically shut out from all doors.The Dalits are one of those.
But it is hilarious to see people accuse the Brahmins for their predicament. Cultural absorption is something all classes aspire to. The Brahmins may have found the means to remain an undiluted and critical social component but to force endogamy on other classes would prove far above their mettle. This is according to the stalwart Dr B.R Ambedkar a Dalit , who authored our constitution.
And now we see those who take the cause of the Dalits seized with impotent rage. And fattening themselves on it.
There are classes among Dalits who enjoyed great economic and social stature a few even rose to become Emperor Like Mahapadma Nanda and the Nanda dynasty.
So in effect the situation could be charitably described as that of a particularly slippery snake and ladder game.
And if you think that the Brahmins had it easy ,Well, think again.
The life within a caste itself is highly controlled and monitored and never more so than for a Brahmin.
A good example is Poet Rabindranath Tagores Grandfather who was ostracised bcz someone in his clan converted to Islam.
Another more tragic eg is my great grandfather who was accused of if having sexual relations with his Gurus wife, when he was a teenager and committed suicide 20 years later when my grandfather was 8 years of age.
And he was demoted to a lesser subcaste. Which like the Tagore family proved to be a blessing!
If you want to see how caste overshadows religion look at this quora comment by a pakistani muslim punjabi
the ruling elite in Punjab was mainly Rajput before the arrival of Sikhs. Many of them converted to Islam and remained Rajput just like my ancestors. When Sikhs came into power most of its people belonged to Jatt tribes and people who converted to Sikhism, whether they were Rajput or not denoted themselves as Jatts.
For instance Barar and Sidhu/Sindhus are also a sub caste of Bhatti Rajput just like Sansi. My grandfather was from a village in Moga called Killi Kalan. Now it belonged to Bhattis and Brars. All Hindus who converted to Islam remained Bhatti and those who converted to Sikhism became Brars.
But the real premise of your OP if I am not wrong is that of the creeping Casteism in America.
Well we have seen a midline split of the electorate in USA.
Fareed Zakaria described the groups without batting an eyelid as thus-
If you hold a diploma or a higher education and live in an Urban area you are a Biden voter. Highschool and non urban population vote for Trump.
The demographics are changing and it is no longer about colour or creed.
Its about clamouring and jostling for opportunities. Just the way things are happening in India.
Look how ML King discovered that he belonged to a Caste when he came to India 😀😀 https://www.newyorker.com/magazine/2020/08/17/isabel-wilkersons-world-historical-theory-of-race-and-caste
For those who gnash their teeth at the way India is not changing to their expectations. I say to them – India never believed in the idea of a linear progression of events ending in a makebelieve world.
The Gods and Demons , the Dark and Light will come
and go again and again.
Like that carousel in ‘A Hundred Years of Solitude’
We will reach the realm of enlightenment then descend into the darkness and come out of it again.
But the important thing to remember
– is to dance 🙏