I guess I’m the only one who has heard of white people calling themselves “crackers”?
White folks who are native to Florida, specifically, tend to use this term in reference to themselves. Florida cracker - Wikipedia
Just to be a pedant: Black people do not just use “nigga” in reference to themselves. For those who use it, it’s often used like “bloke” or “guy” or “folks” is in other English dialects. Like how the Smurfs use “smurf” as a general verb, “nigga” is a general noun. “That nigga Trump is fucking up this country. Niggas are dying over here because of him.” In this sentence, “nigga” does not mean black person or even black people. It means whatever you want it to mean.