I'm married to an Indian born and raised in America. Yet, there are still a few cultural differences between our families. The ones I've faced as a result of being in a relationship with the hubby directly have been minimal--how we expect to be handled after death, for one. The ones I've faced as a result of being in a relationship with his family (especially extended) have been a bit bigger. Don't get me wrong--I love my in-laws, but the father-in-law and I don't see eye to eye on a lot of things. Then again, the rest of the family doesnt see eye to eye with the FIL on a lot of things either. I'll just keep it at he's very set in his ways and often single-minded. A lot of his mannerisms and ways are very traditionalist Indian male (as has been pointed out by several Indian friends).
On the other hand, I have a good friend from Russia who was here on an H-1 visa. She got married this year to a U.S. citizen. I think as a result she will be able to get her permanent residency more quickly than if she were unmarried or married to another non-resident. She's adapted pretty well to the culture here, but that's mostly been because she's been in the States for several years (i.e., since college) and worked to assimilate herself. I don't think she had too many cultural things to overcome by the time she met her hubby and got married. If anything, her kids will get to be multi-lingual.
All in all, I think that generally the longer a person is in the country they are living in the easier it will be to match up with a resident of that country--so long as the person has not isolated him/herself. They will generally have a better idea of how things work and how people in the country think/talk/interact. A lot also depends on how different the cultural differences are and how traditional the person is. The more alike the cultures the faster the persons will adapt to each other. As far as family is concerned, I think it also helps when they are exposed to the cultures. I found that while my in-laws living in the States were generally accepting and understanding of me the extended family living overseas certainly had a lot more misconceptions about how things work here, about people in general, and about me. Likewise, my family had a lot of questions and ideas about the Indian culture when they found out that I was involved with an Indian.
My advice to anyone getting involved in a multi-cultural relationship is to be patient--very patient, and to do what you can to understand as much about the other culture and how things work both in the culture and in the family with whom you will be involved. Those who get involved in any relationship with someone from a different background (be it culture, religion or whatever) will need to learn perserverance.
I don't know if that is the information you are looking for, but that's my $.02.
