If they lived in America, they did. It affected the the prices of the goods they purchased and affected the price their labor could bring. It affected who they voted for, and years later where they would live. The fact that simply by virtue of the state of being white, they were immune to being enslaved within a culture of slavery affected their relationships to each other and to free black men.
>only the top 1.5% (1) or so of Americans enjoyed any of the benefits stereotypically ascribed to "white people."
Bullshit. If you can get a cab and a black man can't, you're enjoying "benefits stereotypically ascribed to 'white people.'" If a job application is turned down because a name sounds black, you're enjoying "benefits stereotypically ascribed to 'white people.'" Not recognizing that is just a sense of entitlement.
>Blaming all whites for slavery is much like blaming all Muslims for 9/11.
Muslims didn't get to vote (and take up arms against each other) to support 9/11, thousands of times in thousands of contexts over hundreds of years, and they didn't get the economic boost that comes from a large proportion of the population existing to serve.