Issues of sexuality aside, this just isn't true. Serving in the military requires team members to trust in each other's professionalism and competence. "Comfort" simply isn't necessary.
Inherent in this is the belief by the group that the rest are just like you and are.
This is completely wrong. The military brings together Americans from every demographic--men and women; white, black, latino, Pacific islander, southwest Asian; Protestant, Catholic, Orthodox, Mormon, atheist; people from other countries like Brits and Africans; patriots and pragmatists; cat people and dog people. Military life forces service members to get along with people that aren't just like them. Most service members are pretty good at that, because they are professionals. The ones that aren't professionals join little cliques and complain about the "Canadians."
“Comfort” simply isn’t necessary.”
Sorry, but that’s not true, it is necessary. Having served in the military, I know from my own experience that professionalism and competence is not enough; one must feel comfortable with other members of the team.
As regards your observation about this nice polygot of various types of individuals being seamlessly molded into one big happy unit, there is an element of truth in that individualism is subsumed to the needs of the unit, but you can be sure that cliques based on color, ethnicity and the like remain. It would be countertuitive if this didn’t occur.
Did you not notice the existence of cliques in your military experience?