Christianity has moved on from being horrible, as in the Middle Ages.
Yes, of course... I get your point.
Jesus readjusted people's thinking regarding Law. The problem was on the inside according to Jesus, not on the outside.... a sin nature that operates alongside of our own will, and many times foreign and antagonistic to it.
The apostate Catholic Church jettisoned the idea of being born again (which is the Christian solution to the problem) once Rome's City Overseer filled the power vacuum when the Capitol was moved away from Rome to Constantinople.
This consolidated power, both religious and secular into one super state. It produced a thousand years of unbelievable persecution against bible believers. (Biblical Christians as opposed to cultural Christians)
The founders of the USA, fresh out of a thousand years of persecution from religious super-states, wanted nothing more than to create a safe place to live according to Christian ideas, free from the heavy hands of consolidated religious and secular authority.
The idea that the government would now allow millions of people to quickly migrate here who aren't even cultural Christians, and would probably like nothing more than to create another religious super state to enslave its opponents, is antithetical to every single founding father of this nation I'm sure.