AHS has nothing to do with the Fox/Disney merger. If it did there would be a much bigger story like Universal suing Disney for breach of contract.
When one company buys another the contracts that are previously in place have to be honored. Is it possible that Disney settled with Universal to get AHS pulled, yeah it is possible, just as it is possible that HHN hired all of the original actors of Stranger Things to play their parts, but not likely.
Also I think UCM is being done becuase Murdy thinks this might be his last shot at doing it.