I basically agree with opebo, a small professional core for highly specialized positions is fine, but otherwise having a standing military is too dangerous, as the American experience so aptly demonstrates.
Hmm.. you mean the imperialism? Or those few occasions when it was used against the subjects? It seems to me that as far as actually punishing the serfs, the american penal system of control has gotten by with only the threat of the military - the police and so forth seem to be quite sufficient for actual use. The foreign adventures have profited the upper class mightily of course, and served to help in deluding the lower class, but I don't know that they were strictly necessary for the enslavement of those at home to be accomplished.
I guess I consider the bloated and corrupt military we have to be less a 'danger' than a miserable side effect of our main illness - the capitalist system.