Well, of course, America should let all comers into the USA. You have the funds and resources to provide the necessary housing, education, health and money to them and their families. And, of course, the bonus is they will vote Democrat once granted the right to vote. It's a no-brainer. 

But wait .....

“Please, try to understand us, your liberal and democratic principles are worth nothing here. You must consider again our reality in the Middle East, because you are welcoming in your countries an ever growing number of Muslims .... Also, you are in danger. You must take strong and courageous decisions, even at the cost of contradicting your principles.

“You think all men are equal, but that is not true: Islam does not say that all men are equal. Your values are not their values. If you do not understand this soon enough, you will become the victims of the enemy you have welcomed in your home.”
(Amel Shimoun Nona, Chaldean Catholic Archbishop of Mosul, Iraq)