Boston bombers were from Russia.  That there have been NO deaths in the US from immigrants from those 7 nations in since at least 2001 says something about the how much of a problem it is, and how much Trump's order is all about show.  If it wasn't just show, he'd have a different set of countries on that list. A few crazy people from those nations having unsuccessful attacks over the course of 15 years, implies no real competent plotting and no conspiracy and just a typical number of nuts that we might see in most any other subset of people in the US.  How many people were killed by non-Muslims in just Anchorage in 2016?  Something like 30+.  It's not like the killers in Anchorage were particularly competent.  You don't need much to actually be able to kill someone, so I  don't get you fear mongering over some unsuccessful attacks over 15 years.