Caste is essentially the same as feudalism, but unlike other regions of the world where feudalism was a societal concept, it became a religious one in India. Buddhism for example is an Indian religion but Buddha was explicitly against the concept of caste-by-birth. Abrahamic religions are also devoid of the concept of caste.
So whenever there are any caste issues, it's always two Hindus involved. Upper caste hindus don't probe the caste of a person if they hear a Christian/Muslim/Buddhist name because they know that it won't exist.
Because of how easy it is to give up caste, lower castes have been doing religious conversions in India in large numbers. The so called upper caste , only make up 30% of Hindu population and if all lower castes were to convert then Hinduism would become a minority in India. To prevent this mass exodus, various states of India have been coming up with anti-conversion laws which make it really hard for people to convert. Though I really don't understand why lower caste dalits in the US continue to stay Hindu, when they could just change their religion and avoid the whole caste discussion altogether.