And as for Asians, you can easily observe the dynamics by first looking at the "yellow peril" scare, or, say, the justifications for the internment of Japanese-Americans during WW2 - and then compare it to how the same groups are treated today. The difference is obvious and immense.
I do agree that "white" is a bad term for it overall. But thing is, it's a pre-existing one - the reason why we talk about stuff like "white privilege" is because "white" and "non-white" was the language used to get us where we are, and the same distinction (usually obscured shibboleths like "inner city youth") is what largely fuels systemic racism today. So it's impossible to meaningfully talk about racism without talking about whiteness.
(I'll also add that SJ vocabulary is pretty bad overall when it comes to conveying concepts accurately - e.g. "privilege" is another highly misleading term that I wish was never popularized to describe the very real concept behind it.)
"What fuels structural, systemic racism" is another can of worms entirely and I see little reason to get into it here, other than to note that our aforementioned attitudes to class, wealth, gratification etc. might just as well be "fueling" other systemic social problems that people don't generally describe as "systemic racism", such as the opioid overuse epidemic among lower-class whites. So again, bringing race into the description of these problems risks adding confusion for little gain.
And yeah, this is the historical meaning of "white". Consider the one-drop rule, both as a legal concept, and as a social convention. You could be white as snow, and yet the moment the society knew you had a black ancestor several generations back, you were treated as black - and thus, you were black. In other societies, it was different - e.g. the Spanish system of meticulously tracking blood percentages, and a formal hierarchy based on that, made it possible to "whiten" a bloodline.
The one-drop rule is no longer a broadly accepted social convention by itself, true. But while it had been, it created numerous derivative cultural markers, above and beyond skin color, which continue to be the basis of the social conventions establishing race today - distinctive names, for example, or use of AAVE. Somebody can still be white as snow, have stereotypically European facial features and hair etc - but if their name is DeShawn or Shanice, and they "talk black", they will be categorized as "black who can pass as white", and treated as such. Scenarios where their appearance isn't in the picture at all - e.g. that famous study with swapping names on resumes - make that rather apparent.
BTW, the opioid abuse epidemic is very much a manifestation of systemic racism - the reason why it started in poor white communities is because they are more likely to get an opioid prescription to begin with, and because the prescriptions are more generous (and thus more ripe for abuse). These both stem from long-standing racial stereotypes - one about blacks having inherently higher pain tolerance [1], and another about them being less responsible and less able to exercise self-control. Ironically, as those stereotypes are getting addressed, the epidemic is starting to affect black communities more.
But you're absolutely right that not every social problem is about racism, even when it stems from some social value that is also used to define race. For example, the overemphasis on "rugged individualism" destroys informal community safety nets regardless of race, and the adverse effect is the same for somebody in the same position on the economic ladder. It's brought up more often specifically in the context of black communities mostly because theirs haven't been destroyed as fully as those in white communities. So the process is much more apparent there to begin with - and then economic effects of systemic racism (i.e. the fact that black communities are much poorer on average) make the negative effects of this destruction much more blatant.
[1] https://www.aamc.org/news-insights/how-we-fail-black-patient...
It's not "objective" or outside of culture - on the contrary, it is definitely subjective and inter-subjective. It's what some people have been expected to identify as for quite some time, "as a social convention". I don't think the current "social convention" agrees with e.g. "Marco Rubio is white because society treats him as white". Not because of the color of anyone's skin, or anything like that - but because he is widely identified as Latino/Hispanic, and a widespread "social convention" treats that as something other than white. (Perhaps this sort of identity is less socially important than it formerly was, but that's quite different from positing a sort of "honorary white" identity wrt. Rubio or anyone else.)
> ...For example, the overemphasis on "rugged individualism" destroys informal community safety nets
Is it really the overemphasis on rugged individualism that does this? Some people might dispute that, and blame widespread dislike for traditional values or traditional community institutions - something that, for better or for worse, seems to be very much part of the "progressive" ethic.
This feels like a just-so story to me. The story of "white" identity as such in the U.S. is really a lot simpler than that, and we can trace it very easily in the primary sources: it does show up early on as something that was talked about mostly in opposition to Natives and the enslaved blacks, and to some extent it kept that role in the "Jim-Crow" segregated south after the emancipation of slaves, up to as recently as the Civil Rights Era. In the meantime, and quite importantly for this discussion, it got actively repurposed throughout the U.S. as a way of assimilating the fractious immigrant identities from Europe into something that could be shared by European-Americans in general. This shows up especially clearly wrt. immigrants from Germany in the run-up to World War I, who were heavily encouraged to shed any association with their nationality for obvious reasons; but the same is true of other nationalities.
But to say that Asians have been subsequently adopted as "honorary whites" in some sort of continuing dynamic, let alone that this is also true of "white Hispanics" (a categorization that does formally exist in the U.S. Census but that very few would acknowledge as such) really strains credulity. I do think that this whole way of talking about "Whiteness" as something terrible is purposely divisive; it is exploiting a deep equivocation about the legacy of slavery and segregation in order to disregard the fact that "white" is what many, many millions of people in the US have been explicitly requested to identify as, and it's really not feasible to disregard or deprecate existing identities like this without being divisive.