By far, the largest # of appointments are charged to US Representatives. 5 for each Rep at each Academy at any given time. (Freshman-Seniors). So it follows that a states population is the main determining factor effecting how many cadets it sends to SAs. TX, where we live has 38 Representatives. OH has 15, PA has 17.
Obviously ea state has 2 senators, ensuring as many as 250 cadets at ea Academy, very evenly spread geographically.
Other factors that may, or may not influence geographical spread, include states that more veterans reside in, leading to Presidential Appointments (100 I believe, to ea Academy). It follows, perhaps, that a state like TX may have more veterans whose children seek appointments, than a state like Wyoming, that just has a lower population. Or any state that simply has a lower per capita veteran population, might be very slightly less represented. There are a few other appointment sources involved, that might not be geograpically driven necessarily, but those #s are relatively small. So appointments are indeed, very much dispersed geographically. It's based on population. That way Academy appointments are a mostly fair representation of the entire country. End result not exactly matching the Electoral College, but fairly close.