It would not be permissible to attend the weddings, funerals etc of a non-Muslim.
Also, it would be Makruh Tahrimi (prohibitively disliked) to enter or even pray in a church, Synagogue, Hindu temple etc, being a place where gross Shirk (sins of polytheism) is committed. Also, according to explicit prophetic Hadiths , such places are the gathering places of devils.