President Trump’s Claim That Foreigners Are Responsible for ‘The Vast Majority’ of Terrorism Convictions since 9/11

ISP's "Terrorism in America After 9/11" data were cited in the Washington Post: 

What do we know about the foreigners’ terrorist threat to the U.S. homeland? The answer: Not what the president claimed.

New America found 413 people charged with or credibly involved in radical Islamist-inspired activity in the United States since 9/11; half (207) were U.S.-born citizens. An additional 87 were naturalized citizens, and 47 were permanent residents.

“Far from being foreign infiltrators, the large majority of Islamist militant terrorists in the United States have been American citizens or legal residents,” according to the New America report on Islamist militant activity since 9/11.