“Cracker” is an actual insult in the American southeast. I know to a Californian or a Brit it must like calling somebody a poltroon or some other absurdly out of date insult.

It’s originally a term of abuse used by rich whites against poor whites in the south. Since been adopted predominantly by black users (and in my experience rich southern whites use “redneck” or “country” where they might have used “cracker” before.