In-laws conflict (edited)

My wife and I come from somewhat different backgrounds and ways of living. I am not going to go into details on that, but will only say this difference often causes misunderstanding and misinterpretation. It took me and my wife a great amount of effort and time to get used to each other's way of living. Just for context, my wife and i live in a different city from our parents, but we always keep in touch with them.

Her side of the family often accuses my parents of certain things, that, at first i am finding hard to believe in. But if i take into account the difference in the backgrounds between my family and hers, it often makes sense to me how certain things are mis-interpreted by either side. On the other hand, i can also see a world where my side of the family is also accusing her side of family, possibly because of similar reasons (conflicts stemming from differences in backgrounds, mentalities, ways of doing things, etc).

As a result, there are some trust problems between me and my wife. Given that there is a history of conflict between our families due to reasons described above, oftentimes my wife does not trust me that I am "on her side", and is often does not like when i am too close with my parents. On the other hand, i don't have any major discomfort with her and her parents. I just try to stay out of it.

These trust problems exist to the point where my wife demands that i only speak with my parents only so that she can hear the conversation, so that she can make sure that my parents are not insulting her or her parents or saying anything bad about her side of the family. I had to make a promise that i will not contact my family privately. On one hand, i can understand her feeling of being "betrayed", on the other hand i really feel torn.

Sometimes deep down i feel all of this is my fault. I failed to appropriately mediate conflict situations early enough. I did not realize in time what this has grown into. I failed to comfort my wife and display my support for her when it was needed. And i don't know how to do it now in the most healthy way that would keep "everyone happy".

Would appreciate any advice on how to deal with the situation.