Difference in national traditions and self-perceptions. *
An interesting observation. I think there is a contradiction in the way American's view themselves in relation to non-western foreign militaries. We do not want to see ourselves as imperialists conquering and subjugating the locals. Therefore we do not like the idea of mixed, Sepoy style forces.

Yet we are a hierarchical culture. We believe that people make their own success and if you are in the gutter you are there based on your own failures. Therefore we still view people in parts of the world as somehow "lesser". You see it in the way we mock their systems as inferior to ours.

It sets up a condition where we do not want to build combined unite with them because that would be colonialist yet we refuse to accept that they can do the job as well as us so we continue to treat them as if they are our subjects.

It is our problem and I don't think we are likely to fix it any time soon.