I know I might be oversimplifying this. But you can legally change your last name. But you cannot change your race. Unless, your phenotype is somewhat ambiguous and can pass as a person of the majority racial group. But that is rare. By conflating casteism with racism, you're diluting the meaning of what racism is and systemic effects it has had on minorities in the United States.

By the way I'm a person of Indian ancestry born and raised in the U.S. According to my grandparents, we're of lower caste as well. But no one has ever asked me what my caste is simply based on my last name. I'm not denying that casteism isn't a problem within the Indian diaspora. But it is entirely different societal problem within the United States compared to racism. In India , it might be similar to racism. But not the same in the U.S.

Let me put it this way - a person who hates all minorities or specific ethnic groups, isn't going to care what caste you belong into. He's going to hate you and the higher caste Indian person equally.