@Drnaline,
Christendom, or Christenhood, in the widest sense, refers to Christianity as a territorial phenomenon: those countries where most people are Christians are part of Christendom. In the West the word Christendom sometimes refers to Roman Catholic nations that include the "Social Reign of Christ the King," the concept that a nation is subject to the authority of the Church.
"the concept that a nation is subject to the authority of the church" can not be implemented in the United States of America because in this country the citizens are the sovereigns and as such are only "subject" to our own authority.
Who gets to pick the church in your vision for a new Christendom, I go to a baptist church, not because I consider myself a baptist, but because my mom goes and I like the band and the message. I consider my self a "follower of Jesus" more than any religion.
subjects are SLAVES! you only like the idea if it's YOUR church.
...and dont forget that if the church was able to maintain the dominance it throughout the middle ages we would still be the center of the universe living on a flat earth.