I live fairly close to the other border. I've been hearing news reports about how many Canadians went over to join ISIL. Estimates are around 100 or so; they don't know for sure.

Seattle's population is fairly diverse and fairly apathetic to the current situation in the Middle East.

Vancouver B.C. has a large East Indian and Pakistani population and Middle Easterners would blend right in.

Just saying, if a terror attack wants the most attention, go where people won't expect it and where security is lax.