Why are people assuming the DiL is controlling? We only have the OP's word for that, similarly. the OP says
family members he still talks to who say that she is angry at him, stops him from having hobbies and friends. She refuses to let him see even the other side of his family more than once or twice a year.
These are the words of a bitter and angry woman. I wonder how far she is putting words in people's mouths, or just hearing what she wants to hear, regardless of what family and friends actually say. Having been a victim of such mishearing myself this year, although not in a family context, I have seen how this happens.
Both UK and the USA has a culture based on the teachings of the Christian religion and there is a quote from the bible that sums up quite clearly the relationship between an adult child and their parents after the child forms their own personal relationship and sets up their joimt home with their partner. It says:
For this cause shall a man leave father and mother and cleave to his wife and they twain shall be one flesh, wherefore they are no more twain but one flesh. What therefore God has joined together let no man put asunder.^
Matthew 19:5-6, King James version
In other words when an adult child forms a relationship with another person and they set up their own household, then that is their primary relationship and we, parents, must back off.
That is what the OP needs to do.
Most GN members will try to be kind and understanding of those who file problems, but this does not preclude us calling out someone whose expectations and demands are unreasonable and telling them that they are the cause of their own problems.
As far as I can see that is definitely the cause here. However in doing this I am not criticisingor demeaning the person, I am critiising their actions.