It's clear to me that, in American society at least, the majority of bisexual men are to be found among the ranks of men who would never identify as anything but straight

As I've said elsewhere, possibly even on this thread... if my culture makes it more difficult for men to identify as queer than as straight, then even if sexual orientation varies (like many other things) continuously within the population, I should expect the majority of more-than-negligably male-oriented men to identify as straight.