I think this is one of the core questions that those playing identity politics games completely ignore. The very nature of their own efforts is, itself, something-ism. As you illustrate, they're categorizing a whole group, and assuming that every member of it fits its stereotypical mold.
So in one respect, sure, as a white male I had some advantages, but there are plenty of other ways to look at it. As a "nerd" I was bullied; I suffer from an incurable disease; I'm not a particularly attractive person; I'm notably uncoordinated and bad at sports. And on the other hand, I've got a fairly sharp mind, and have some talents and a supportive network around me. A lot of these things apply to other people in and out of my demographic cohort, to such a degree of ... let's say "diversity" ... that it makes no sense to focus on those demographics when thinking about who has privileges or disadvantages.
Privilege, favor and advantage is completely useless single-dimension concepts when talking about demographics. Statistics can show that men dominate the highest and lowest ranks in society, but every only focus on the few top who succeed and turn a blind eye to everyone else. It as if we would argue that people who gamble are "favored" since they have a slightly higher chance to become millionaires compared to everyone else.
White males has comparably poorer supportive network than most other demographics. Culture assume that all white men are healthy and strong, and society carry a discrimination when reality crash with that imagine. Is that privilege? Privilege for whom and compared to what?
Perhaps, perhaps not -- but your examples do nothing to counteract the idea that it is, as every single one of the groups you've mentioned is, in the US, significantly advantaged over the broader, corresponding group that is identically described without the "white men" or "white male" limitation.
Now, in many case, the system is also stacked against the class described in the other part of the descriptor, such that the intersection of that class with the "white men" restriction is disadvantaged compared to "white men" more generally.
But that doesn't, in any way, change the fact that the system (in the US) is stacked in favor of white men.
> Why is it OK to assume the system is stacked in someone's favor?
There is a difference between "conclude" and "assume".
> How is that not prejudice?
If you assume in the absence of evidence, it is prejudice. If you conclude on the basis of evidence, it isn't prejudice (because there is no "pre".)
Is it? What about white men who grew up as orphans? Or with parents that had severe mental illness? What about white men with emotional disorders?
What about white male cancer survivors? Or white male single parents?
What about white men who grew up as historically disadvantaged minorities in their home countries?
Why is it OK to assume the system is stacked in someone's favor? How is that not prejudice?