There are domestic extremists of every stripe. The ones that are really high on the FBI watch list are the ecoterrorists. Right behind them are the right wingers and religious fanatics. But overseas it's the jihadists who are number one on the hit parade.
This doesn't mean every Muslim is a terrorist. But let's face it, the majority of terrorists outside the US are Muslim. I try my best to be objective and not paint all of a group with the same brush, but facts are facts.
From http://www.fbi.gov/stats-services/publications/terrorism-2002-2005
In keeping with a longstanding trend, domestic extremists carried out the majority of terrorist incidents during this period. Twenty three of the 24 recorded terrorist incidents were perpetrated by domestic terrorists. With the exception of a white supremacist’s firebombing of a synagogue in Oklahoma City, Oklahoma, all of the domestic terrorist incidents were committed by special interest extremists active in the animal rights and environmental movements. The acts committed by these extremists typically targeted materials and facilities rather than persons. The sole international terrorist incident in the United States recorded for this period involved an attack at the El Al ticket counter at Los Angeles International Airport, which claimed the lives of two victims.
The terrorism preventions for 2002 through 2005 present a more diverse threat picture. Eight of the 14 recorded terrorism preventions stemmed from right-wing extremism, and included disruptions to plotting by individuals involved with the militia, white supremacist, constitutionalist and tax protestor, and anti-abortion movements. The remaining preventions included disruptions to plotting by an anarchist in Bellingham, Washington, who sought to bomb a U.S. Coast Guard station; a plot to attack an Islamic center in Pinellis Park, Florida; and a plot by prison-originated, Muslim convert group to attack U.S. military, Jewish, and Israeli targets in the greater Los Angeles area. In addition, three preventions involved individuals who sought to provide material support to foreign terrorist organizations, including al-Qa’ida, for attacks within the United States.
Whereas the violent global jihadist movement manifested itself primarily in terrorism preventions in the United States from 2002 through 2005, internationally the movement claimed major attacks against U.S. and Western targets that resulted in American casualties. Most of these incidents were perpetrated by regional jihadist groups operating in primarily Muslim countries, and included attacks committed by Indonesia-based Jemaah Islamiya and al-Qa’ida in the Arabian Peninsula. The coordinated suicide bombing of London’s mass transit system by homegrown jihadists, however, brought the violent jihadist movement and the tactic of suicide bombing to a major European capital.
But unfortunately all over the world, just like in this country, the vast middle never gets into power. Only the far end of the spectrum zealots have the 'fire in the belly'. 
