TRUMP: Saudi Arabia, Egypt and Turkey left out of the order? Most of the 9/11 conspirators came from Saudi Arabia." Truth-o-meter

http://www.politifact.com/truth-o-meter/statements/2017/jan/29/jerrold-nadler/have-there-been-terrorist-attacks-post-911-countri/

"Far from being foreign infiltrators, the large majority of jihadist terrorists in the United States have been American citizens or legal residents. Moreover, while a range of citizenship statuses are represented, every jihadist who conducted a lethal attack inside the United States since 9/11 was a citizen or legal resident," the New America study says. "In addition about a quarter of the extremists are converts, further confirming that the challenge cannot be reduced to one of immigration."