I am not saying caste discrimination doesn't exist. But as an Indian American living in the United States for 20 years, I can tell you that I have never seen/experienced/practiced it here in the US and I will not let anyone do it either on my team (I run a company) or personal family/friends. Having said that, it is a very common joke among a group of Indians when they get together about the whole "vegetarian" vs "non vegetarian" thing. You can argue that it is bad to joke about this topic but it has nothing to do with caste or religion. That's what I am saying.
Are you yourself higher caste? Being a member of the group that isn't discriminated against frequently makes it harder to see the discrimination. My wife is Indian-American, and her parents are a mixed-caste marriage; I've seen caste bias between her own relatives, even though they're all in the US and have been since the 1970s.
You not experiencing it does not mean it does not exist. Please see other instances besides "vegetarian" argument where it is blatant.