> Is it unfair to compare the median white american to the median Japanese, just because the U.S. also has a large Hispanic population that mostly descends from low-education post-1970 immigrants from impoverished Latin American countries?

It's a bit unfair because the average white American is wealthier than the races you excluded from American. The average Japanese person includes everyone from all classes, it does not skew towards the wealthier. If it did, you might see a different result.

Like I asked, does the comparison hold if you segment the results by economic class?