People who don't accept the teachings of the Church (as Hitler did) automatically excommunicate themselves. They can return to the Church through confession and penance, something that Hitler never did.
The Church was one of his worst enemies, and he regarded Christianity as a "slave religion." He was very devoted to Gnosticism and the occult, what we would now call New Age; in fact, it was from the occult tradition (including the Freemasons) that he got the swastika that was his regime's symbol.
He was also very much into a pre-Christian ethos, or what he thought was pre-Christian.