The SAs, to a greater extent than most colleges/universities, have huge demographic range. Among other things, board scores help USNA "compare" a candidate from a 100-person school in northern Maine to someone from a 4000-student inner city school in Los Angeles to a candidate from a private Catholic school in San Antonio, Texas.
However, as you can well imagine, there are many, many other elements of each person's application. So, the SAT/ACT provides a data point. How much it counts is, as Time2 stated, not something anyone here knows.
You should also consult with your BGO. Experienced BGOs have a pretty good idea of the scores that GENERALLY are needed to be successful in that geographic region. That knowledge can help you decide whether to retake or not. (As an aside, some will say retake until you achieve perfection. As a practical matter, if you stand at 750/750, you have to question whether it's really worth the time and money for the potential incremental improvement).