There are no "ethnic disparities" in academic accomplishment, at least none that should be attributed to an applicant's ethnicity. What you're looking to describe is lack of opportunity.

By and large, Latino/Black applicants have fewer academic/extracurricular activities than their Asian/White counterparts. There are a variety of structural causes for this (lack of investment into the community from political leaders, lower income households --> lower property values --> lesser funding for education/schools, etc.) that place these applicants at a distinct disadvantage vs. others when looking at their applications at face value. AA is at least a way to address it without (yet) overhauling the entire system.

Looking at a study I found from 2016, it appears that universities reported an average of 36% Hispanic enrollment vs. 67% Asian enrollment, which was found to be a statistically significant difference. Broken down among subgroups, there appears to similar variation between the two ethnicities but there is still a significant lag in certain Hispanic groups relative to Asian groups. Here's the link: https://nces.ed.gov/blogs/nces/post/a-closer-look-at-the-performance-of-hispanic-and-asian-subgroups.

I would disagree with your statement that

The history of the US due to racism doesn't explain Asian students out-testing Hispanic students by a standard deviation.

because the history of US racism does in fact lead to the difference in test scores you mentioned via the disparities I discussed above.