I think the fact that we have to vigorously study gender variances in men and women allows us to notice the small idiosyncrasies between the two. Most non-trans folk do not have this ability. Thats why its easier to be "clocked" by another trans person because they themselves struggle with portraying the right gender behaviors.
Also, ive highly considered moving to Thailand for that sole purpose. Finding acceptance. Its as common there as rain in Seattle. I most definitely want to at least visit Thailand in the near future. Believe it or not, i have never met an out or transitioning transsexual in person. I know several "feminine" gay men and "masculine" lesbians, one specifically who i could swear is trans (ftm) but not outed herself. She and her partner are having a baby and she is all over FB saying she is the "daddy" and i couldn't agree more.