UPDATE: A friend of mine weighed in via email:
I always figured it would be easier to find someone I get along with on the axes I consider most important to me (intellect, humor, modern liberal sensibilities) and adopt the few dishes and holidays I want to keep than it would be to find someone whose main identity is Vietnamese/Asian and hope that they fulfil the multiplexity of what I want in a partner. Unless it's really important to you to share language and culture and traditions, you're going to spend a vast amount of the day talking about things other than "hi five! we're both Vietnamese!"