My cousin, who is American-born, worked as a waitress in a Chinese restaurant. Once, a white woman who was unhappy with the service asked her sarcastically, "Do you have your green card yet?"
Many non-Latino white and black Americans assume that all Latinos and Asians are "immigrants", even if the people in question are American-born. And there are many people even more ignorant than that nasty customer - many Americans do not even know that there is a distinction between legal immigrants and illegal immigrants. When angry native-born Americans look for "illegal aliens" to beat up, they usually don't ask to see someone's immigration papers to determine if that person is a legal or illegal alien.