If we can’t ban islam we can certainly ban immigrants from enemy states or states that harbor terrorists or societies that wish to destroy us.
Commonsense.
Yes we can. All "we" need is the political will, which has been sorely lacking.
True, though with how things have gone the past 20+ years, you'd have to ban immigrants from most of Europe, and I doubt any President (Trump or anyone else) would be willing to do that.
Perhaps the best solution would be what some in this thread have suggested - just institute a moratorium on immigration, period.