The UK-Based Henry Jackson Society has released a comprehensive statistical study of US-based terrorism entitled, Al Qaeda in the United States-a complete analysis of terrorism offenses. It is authored by Robin Simcox and Emily Dyer. The below link contains an abridged report. You can also order the complete report. In the below report, a demographic breakdown is given as to the offenders in US cases of terrorism (native-born, foreign-born, converts to Islam etc.).
Hopefully, someone will pass along a copy to John Brennan, the clueless soon-to-be head of the CIA.