The Church is clear on her definition of marriage: it's a lifelong, exclusive union between one man and one woman that must be open to the creation of new life. That's not the same definition our culture is embracing, although that's nothing new. It's not even a definition that all American Catholics embrace . . . although that's nothing new, either.
And, as of June 26th, it's not a definition supported by the Supreme Court of the United States.