Unfortunately I think those statistics are unreliable. I fully agree that outsiders (e.g. Al Qaeda) have done miniscule damage in comparison to, say, the tobacco industry.
But if you want to look at the history of terrorism in our country, don't look to Al Qaeda or whatever. Start closer to home, with the Ku Klux Klan. They were unequivocally a terrorist group; indeed, their entire raison d'etre was terrorism.
As I pointed out in a thread yesterday, here [1] is an example of homegrown terrorism, absent from your list. Ben Tillman [2], who played a leading role in the murders (or, at least, who claimed to; perhaps he was too chickenshit to do his own dirty work) was rewarded for his efforts by election to the South Carolina governorship and, later, the United States Senate.
African-American participation in voting in the South was virtually nil from around 1880 to the 1960's. Why? Terrorism played a major role.