are domestic students benefactors of affirmative discrimination-type programs? probably, and most likely almost certainly post-crisis when tarp was around.
however, they're also probably at a disadvantage when it comes to preparation since the us education system thinks it's more important that you feel good about spelling the word cat "katt" than it does the fact that you spelled it mind numbingly incorrectly.
all that said, it's the same with other affirmative discrimination programs in the us; programs take on underprepared domestics at their own peril, as these students will probably have trouble with the curriculum.
Perhaps part of the reason they are accepted at a higher rate is that they might be more likely to succeed afterward due to the ease of assimilation into American business culture even if they don't have the same level of preparation going into the program.
If all things being equal, domestic applicants will be more attractive to programs because
1) There is no visa issue so much better job prospect
2) Better English (duh!)
3) Can be used on marketing materials which attracts more domestic and foreign students alike
4) Diversify the student body
5) More attractive to prospective employers because like it or not, people want to hire someone who look and sound just like them
The list goes on.
Now, "all things being equal" is a very big catch and I expect some programs will scarify a bit of quality to attract domestic students.
So if you are a domestic student and read these unspoken truth, how would you take advantage?
1) There is no excuse for you to not have a great GRE. If you get a 750Q GRE, your color be damned, they are not that into you.
2) Market yourself as a quantitative person who is a career savvy. This means fill your transcript with worthy math/CS courses.
3) Become a frequent reader of industry magazines like WSJ, FT, Economics
4) Become a member of all the quant community and participate in them