Since cultures evolve over time depending on how much contact a group of people have with others, the more important question to ask is:
"Moving forward, how will Hmong in America identify each other as Hmong?"
When you think about the Hmong in China, for example, many of them practice the same religion/customs, dress in the same fashion, eat the same diet, and pretty much have the same lifestyle in terms of work. There may be those who have fully assimilated into mainstream but for the most part, many of them live in their own remote villages.
However, Hmong Americans are vastly different and with more interracial coupling, many of those children will cease to have dominant Hmong genes. I mention that because right now it seems that we are purely acknowledging each other based on biology. But in the future our descendants will be total strangers and view one another as just a nameless Asian (or biracial person).
As a people with no country, we only have our customary practices to bind us as a people. The day we let go of this is the day we no longer have use for one another. This is one reason why Jews remain in tact. They have customary laws and practices observed only by them. A Jew doesn't marry a Hmong expecting the Hmong to know, understand, and find value in Yom Kippur. Despite many gentiles converting to Judaism, it isn't the same thing as being a cradle Jew - ethnically and religiously.
For example, let's say none of us practice the customary rituals of a traditional Hmong marriage. Then what use do I have of you when I can go to any secular non-Hmong to perform a marriage rite? However, if I find value in the mejkoob, wedding negotiations, bride token, dowry, etc, then I have to keep close to my Hmong community. They are the people who understand the ritual, the process, and the value.
If I don't care about these customary practices then I will be a Hmong in name but not a Hmong in practice. This means I don't need to be tied to any Hmong or Hmong community, but I am still Hmong because my DNA says so.
This is the same reason why LGBT community is upset with marriage. They don't feel that they should have to go set up new rules, new values, and a new process to solidify their couplings. They've already been conditioned to accept the conventional practice. They want to be a part of it.
Yet, we have many young Hmong who see no value in a Hmong traditional marriage. They want to do all American but even that is a fake because they don't really understand all the cultural implications of a white wedding. They are only enamored by the commercialized version of it. The same way that many non-Germans - including Christians - celebrate Christmas with a Christmas Tree.