Currently 36 countries allow gays, lesbians and bisexuals to serve and 22 of the of 26 NATO countries permit them to serve. The United States as most of you know, allows gays, lesbians and bisexuals to serve as long as they keep it secret and are celibate. Countries that ban open service for gays, lesbians and bisexuals include the USA, Cuba, China, Iran and North Korea. See more on Wiki here.
A study on the acceptance of LGBT members in the Canadian Military was published in April 2000 by Aaron Belkin and Jason McNichol. Belkin was the Director of the Center for the Study of Sexual Minorities in the Military at the University of California, Santa Barbara. McNichol was Doctoral Candidate in Sociology at the University of California, Berkeley and Director of ELM Research Associates, a non-partisan research firm in Berkeley when it was published.
The study found
* Lifting of restrictions on gay and lesbian service in the Canadian Forces has not led to any change in military performance, unit cohesion, or discipline.The reports conclusion is that allowing LGBT folks to openly serve did not undermine Canada's military or cohesion.
* Self-identified gay, lesbian, and transsexual members of the Canadian Forces contacted for the study describe good working relationships with peers.
* The percent of military women who experienced sexual harassment dropped 46% after the ban was lifted. While there were several reasons why harassment declined, one factor was that after the ban was lifted women were free to report assaults without fear that they would be accused of being a lesbian.
* Before Canada lifted its gay ban, a 1985 survey of 6,500 male soldiers found that 62% said that they would refuse to share showers, undress or sleep in the same room as a gay soldier. After the ban was lifted, follow-up studies found no increase in disciplinary, performance, recruitment, sexual misconduct, or resignation problems.
* None of the 905 assault cases in the Canadian Forces from November, 1992 (when the ban was lifted) until August, 1995 involved gay bashing or could be attributed to the sexual orientation of one of the parties. Link to study results here
Given that the USA and Canada work so closely exchanging officers to facilitate understanding and working relationships, I wonder if an open queer Canadian was ever put in charge of and American military unit...
update: from National Defense Research Institute (U.S.), United States this report from 1993 - Sexual orientation and U.S. military personnel policy: options and assessment
page 77 deals with the Canadian experience shortly after discrimination was ended against queers.