I will also follow up my comment with a short description of countries in Trumps executive order:

Iraq:  Filled with terrorists including ISIS, Al Queda, Mujhadeen and a variety of violent Muslim extremists.  The US spent trillions after the fall of Saddam mostly trying to stop people from killing eachother in sectarian violence.  The government is corrupt and siding with Iran.

Syria: The mess caused by Obama, Qatar, Saudi Arabia and Turkey has left the country filled with well armed violent extremists, including Al Nusra (a division of Al Queda), ISIS and a variety of other groups.

Yemen: The staunch allies of the US, the Saudis, have been funding extremist terrorists there for years now, including Al Queda.  The place is a disaster zone with no political system even left.

Iran: A country persuing nuclear weapons, funding Hezbollah, that recently abducted US sailors, that has called for the destruction of Israel and the United States.

Hmmm.  Should I go on?