Consider this: the armed forces in Europe have been having gay soldiers, even open gay ones, for a very long time now and somehow they manage to work together and get their jobs done. It seems to me this has more to do with prejudice against gays than any harm gay soldiers could possibly bring to the force. Such prejudice is out-dated and not in keeping with progressive thought and the modern civilization.
The armies of most European nations are vastly different than the armed services of America--from the way they operate to the way the troops live. You are comparing apples and oranges.
Or perhaps Europeans have discovered that a soldier's sexual orientation is nobody's business and that it has no bearing on that soldier's performance or behavior. Which is the more likely and logical conclusion?