The LaFree Report put together for the DHS needs to be understood in its proper context, it is nothing more than an attempt to justify further expansion of DHS activities. http://start.umd.edu/start/publications/research_briefs/LaFree_Bersani_HotSpotsOfUSTerrorism.pdf
It is not an attempt to arm policymakers with facts to think about when making policy, it is not an attempt to show that domestic terrorism is an extremely rare event, it is nothing more than a bureaucrats justification for more funding to do more intrusion to get more data to get more funding to do more intrusion.
Now you can argue that by including world terrorism statistics they are not looking at just the American populace to build a threat matrix. That is complete and utter bullshit, DHS doesn't do foreign threat analysis, so the only thing they CAN focus on is Joe and Jane taxpayer. Trying to make a document that covers terrorist threats against the US, and then completely ignoring the other 200 odd countries on the planet that may have an axe to grind against the U.S. is something only a fool would consider a good idea.
Over 6 billion people on the planet and they want to put the microscope on 300 million. That is putting the microscope on 1 American and ignoring 20 other threats. Hope that puts it in comparison.