Me and my wife come from different countries with very different social norms and expectations (Russia and Spain). We live in Germany and handle the differences between us rather successfully as we try to adhere to the norms of our new home. We also speak German at home (obviously both non-native speakers).
Where it definitely does not work is the relationship with my parents. For me they are part of the family, for her - respectful relatives keep distance. According to her, they visit too often, stay too long, give unasked advice (which is all ok from my point of view). I've tried to adapt to the needs of my partner and made them come not so often, tried to explain that speaking their mind in some situations is not acceptable and "respect because of age" doesn't count.
Whatever I do, my partner seems not to notice. It's either too little, or too late, or something that doesn't need explanation anyway. I didn't react right at the moment, didn't protect her and sided with my parents, and stuff like this. She thinks they intentionally ignore her opinion and do as they please. However if I often don't recognize some situations as bad for my partner, how can they? I can change, but it's unlikely they will. Not because they are bad, but because for them the definition of "respect" and "social norm" is different.
The situation is really bad if we see the opposite things as taboos. Example: at one point in time my parents had to stay in the hotel in the city where we live when we were not there. My expectation was to leave them the keys, for me it's a general taboo to send parents to hotel if our own apartment is available (when we came back, they moved to our place for the rest of their stay). My partner sees it as taboo if somebody visits when the hosts are not at home, so she refused to give the keys.
How can I handle the situation if in conflict cases I agree with my parents? I kind of understand I should side with my partner, but if I do so, it's kind of hypocrisy and I get an inner conflict with myself. I feel ashamed of my actions. I tried to communicate this to my partner, how important it is to me, but got a no, because it's unacceptable and disrespectful to us, and people don't do it this way, and it was bad of my parents to event ask, and why aren't I thinking about our family and not making the interests of our family higher than that of my parents.
It's just one example, there are plenty.
How can I communicate to my partner that she doesn't have the monopoly on truth, and that "respect" can be seen differently in different cultures? How can I explain that she cannot expect that my/our relations with my parents cannot be modeled only on her expectations of what is good and what is bad?