"White" was basically a concept made up by the bourgeois centuries ago to prevent indentured and poor whites and enslaved blacks from realizing they were on the same side economically and socially and revolting together. It characterized the ruling class as a sort of standard that lower-class whites could live up to- gave them a taste of power- and thus racial divisions occurred.
Once you understand this, every racial issue in America logically follows: You understand why different European groups like the Irish and Italians were forced to leave behind the depths of their cultures for the security of being considered "white." You understand why Asians even tried at all to legally argue in court that they too should be considered "white." As a result of this attempt at assimilating all of these different cultures and peoples down into this one thing called "whiteness" or "white culture," you understand why even most white people can't actually tell you what "white culture" is, a peculiar problem not faced by ethnic minorities like black people, Latino groups, Asians, and natives.
You understand why white people will, on average, see other poor whites (like those unfortunate coal miners) as undeserving victims of an unfair system while poor blacks are just lazy welfare queens and poor Latinos are all illegals who are undermining proper work standards and diluting the gene pool. You understand why the nearly free land and money grants given to white people by the government throughout this country's history are not considered welfare, while welfare initiatives that work to include minorities too are indicative of "handouts" and "entitlements" that they don't deserve. You understand why white people love the ACA but hate Obamacare. You understand why white people overwhelmingly voted for Trump while most other ethnic minorities- even those who face the exact same kind of economic dead ends that poor white people do- voted the other way regardless.
And finally, you understand why people who look white regardless of them actually being of Iranian descent like JonTron will basically throw themselves on the spear and turn their backs on who they really are to defend whiteness. Because ultimately, "white" means power, and the long and short of it is people don't want to give up their power.