Sure, the US society should strive to eliminate caste-based discrimination occurring in the US.
But that it occurs in India does not mean that it’s been carried forward in the US.
A history of discrimination leading to a disadvantaged position today, and as a result needing additional support, is a separate problem — an argument for affirmative action — but ultimately is nothing different than all the other classes of peoples who’ve been fucked by history struggling to find security in the US (that is, any solution to the problem is not really particular to Indians, or the caste-system).
It doesn't mean that, certainly, but it seems plausible that it would be, to some extent. And while some lower-caste Indians in the US don't believe they've suffered caste-based discrimination, other do. So... it's here?
It's a hell of a deal with the devil they have to make: put up with the same discrimination they suffered at home, but without any kind of social support network, in exchange for the possibility getting a green card 10 or 15 or 20 years down the road and thus gaining some security residence-wise.