Actually, why not start by banning people from Saudi Arabia, and then putting the Saudis on notice that America will withhold any military support or protection to them until they can convincingly demonstrate they've cut off funding for radical madrassas all over the Muslim world and cracked down hard on their citizens (and government) channeling funds to terrorist organizations (including those actively trying to kill US military personnel).  Y'know . . . something that would make a real difference in the world and really make Americans safer (even if it would require more effort and leadership than another Drumpf publicity stunt for the rubes . . . though I suppose that might be more leadership than Tiny Hands can grasp with his little sausage-like fingers).