"In Saudi Arabia and Iran, everybody is required to live as a Muslim. I see no reason why we shouldn't do the same thing in America,"
Well then, you need to get those eyes checked as you lack the "vision thing."
"which is a Christian nation"
No. The U.S. is a secular nation with a Xian majority.
"established by Christians,"
Some of the founding fathers were Xian, but many were not. Many of the most prominent were deists, deists being something of the agnostics of that era.
"for Christians."
Founded as a secular nation, the U.S. is for persons of all religions and no religion.
="As a Christian nation, we can (and should ) require everybody to live as a Christian"
You are basing you assertions on an incorrect premise. THE U.S. IS NOT A XIAN NATION.
"or at least offer a higher class of citizenship to Christians."
Conveniently forgetting anything to do with equal rights.
"People who do not want to abide by established Christian beliefs and norms are free to live elsewhere. "
Or, try this. People who want to change the U.S. government for the benefit of believers in one particular religion or for the benefit of religious persons over non-religious persons, are free to live elsewhere. You're the kooks, the nuts and the assholes, why don't YOU move?