The Trump administration’s executive order halting immigration from seven Muslim-majority countries was trumpeted as protecting Americans from the threat of terrorism. However it is more likely to end up fueling the narratives of extremist groups fighting the United States. There are reports of Daesh (ISIS) celebrating the Muslim bans.
Banning heavily vetted visitors is unlikely to have much effect on the extremely low incidence of Jihadist inspired terrorism in the US. However, the purpose it does serve is the Steve Bannon agenda of bringing on “the clash of civilizations”.
Likewise, the purpose of Daesh terrorist attacks in the west is to create polarization. Islamophobes like Bannon want to assist that process.