Unless they were paying ISUS, I don't think there are that many. One good way to bring the FedGov hammer down on them is mass murder terrorism.
One guy with either a clean record or traveling on the passport of someone with a clean record gets into the US. Legally, sneaking across the border, whatever.
Either receives a bunch of money in country via bank withdrawal/wire transfer/Western Union or brings it in with him. Norks are poor but a couple million is chump change for any state regime.
Hooks up with a local violent group, outlaw bikers or street gang or whatever. This would probably be the most difficult, but it's doable especially for groups involved in arms smuggling.
Pays them $X00,000.
Local thugs goto an elementary school in Bumblefck East Dakota. County school so 4-500 students, but still a relatively small building with limited egress.
Block or bike lock all egress routes.
Dump large quantities of accelerant inside and light.
Bonus points if they have externally accessible sprinkler mains that you can disable, many do.
Leave one guy with a rifle to shoot up the volunteer fire department truck, the two deputies that work in that county, and other first responders when they show up.
Cheap, easy, deniable, and I'm willing to bet a few hundred little kids getting burned to death would have as much or more emotional impact on Americans as 9/11.
The only reason we haven't seen attacks like this are because so few of the major terror orgs have native Americans on the payroll. The jihadis keep trying for elaborate schemes against heavily protected symbolic targets. My big fear with ISIS is how many Westerners are joining them. Only a matter of time until we see a Beslan or Mumbai or Nairobi in America.
