Christianity had some to do with the fall of the Roman Empire, as did the Romans beming more open and accepting to other cultures, and allowing them to become Roman citizens. Much like we're doing with the horde of illegals coming across the southern border. Romans became fat, bloated, lazy, and more tolerant of other cultures, much like we have.
I was brought up in a Christ-believing atmosphere, but I do have respect for the pre-Christian era of Rome. They ran a tight ship and knew how to deal with any resistance. The Roman Empire at the height of their power didn't fuck around. They had no qualms about lining the roads leading into Rome with the crucified bodies of anyone and everyone who threatened the sovereignty of their domain.
The American empire on the other hand, has just about ran its course.