Hi Way2Complicated & Welcome.
I don't know your personal situation in detail, however let me simply try to answer your questions from my perspective. Yes, it looks like our situations are similar in that we are from a different culture, whilst OP is from the same as WS. Personally, I always found the fact that we are from different cultures very rewarding. Both my wife and I grew enormously, by better understanding the own culture, the other culture, the world. That's the good side. The bad side, is that, in addition to personal problems/differences, the cultural gap introduces additional misunderstandings and mistrust. And this is not helpful in situations like ours. The other very important factor is that my wife is torn between her own cultural background and mine. She was packed away as a young child of 6 to a special boarding school in another city, was educated in a secular and western-oriented way, and saw her parents only twice a year. Her family and cultural background is otherwise quite traditional, with all peaceful and family-oriented Islamic values. Now, she's married to me and torn between life here and something she is missing, something she never had, something she was denied whilst being a child. Comes along OM, that [censored], presses a few 'cultural' buttons and off they go, suddenly everything feels so "homy", comfy, familiar etc etc, OM's mum suddenly becoming the MIL she always wished she had etc etc etc. The frustrating thing is, it's a) all fog because it's an affair and b) it's something I can't compete with nor want to compete with. In short, it’s all a sort of a shadow against which I feel utterly powerless. Does that sound familiar to you? In this situation I agree with you it is a mountain to climb. But no, I don’t hate her culture at all, au contraire, I like it very much and feel very much at home there. Her relatives all like me very much, and I like them too. First we lived in my home country, but eventually moved to London. I hoped that us being both in a culturally "neutral" third place would make it easier. In a sense it was, in a sense it wasn't. Both she and me are 'strangers' here - but through work etc. I managed to quickly form a network of friends. She on the other hand never tried to do that in the first place, only some colleagues from her country with whom she always has/had a love-hate relationship and never was really close. And all the neigbours, other children's mums etc are either all stupid, selfish, racist or a combination of it (she says). Let me ask a few questions: where is your husband from? Where is his circle of friends from? How are women/mothers treated where he is coming from? Why did he settle in the US? Where does he feel he belongs to? Did you learn his language? Which language are you speaking at home? All this of course plays its part in terms of setting excpectations etc. But again, in hindsight, I have to say that both my wife and I learned so much and gave each other so much from each other's culture that we both now can swim like a fish in the water over here and over there. And our daughter too!