A lengthy article reviewing home-grown terrorism in the USA:
My conclusion should be generally reassuring to Americans: Muslim homegrown terrorism does not at present appear to constitute a serious threat to their welfare. Nor is there a significant analytical or evidentiary basis for anticipating that it will become one in the near future. It does not appear that Muslim Americans are increasingly motivated or capable of engaging in terrorist attacks against their fellow citizens and residents
That also cites former National Intelligence Director Dennis Blair’s characterization in February 2011 of violence
..from “homegrown jihadists” as “sporadic,” in which a “handful of individuals and small, discrete cells will seek to mount attacks each year, with only a small portion of that activity materializing into violence against the homeland.
Link:http://belfercenter.ksg.harvard.edu/...ed_states.html