This is an interesting question. Transsexualism has always interested me in an academic sense long before I ever saw any adult videos or pictures of a woman with a penis. I've yet to see Trans America, but have been curious.
This is similar to the crossdresser who takes his wife or girlfriend to a drag show then tries to use it to tell her he crossdresses and is like the performers, which he probably isn't at all. Drag performers are mostly gay men who are campy send-ups of women. That's not what a crossdresser is, and it frequently sends the women screaming in horror.
I don't think there really are any movies that deal with folks like some of us who regard ourselves as male or male-ish or somewhere in the middle, maybe crossdress a little or partially, as opposed to going full en femme (it's been a while since I have because it is a lot of work and the desire isn't all that strong since I lost my sex drive in 2005), and just want to sort of be somewhere between the two extremes. Even the movie Just Like a Woman with Adrian Pasdar doesn't really fit who I am.
I don't remember if Trans America won any awards, but if it did, you could always just say you want to see it because of that or because you've always liked Felicity Huffman. You might also have to reassure your wife you aren't planning on fully transitioning, and you just wanted to see this movie because it looked interesting.
My (now former) fiancee got pissed because I watched a British series about a bunch of transsexuals, both FtM and MtF, in various stages of transition and of various ages who got together on weekends for a summer. There was no nudity or sex, but she was pissed.
You might be better off watching it alone unless you're absolutely sure your wife won't freak out or disapprove. Be prepared for her to keep hitting you with questions months down the line because it is my experience that "bitches be crazy" and thoughts just race and go around and around in their minds even when we think an issue is settled. Nothing ever seems to be settled. Just my two cents. You should know your wife by now.