Who says they would need to smuggle the material into the USA!Quote from pspr:
But Big Sis is right there to take credit for stopping them and say "the system works". I can't stand her.
I would guess Paris is the most likely place for the first dirty bomb. They don't want to risk trying to get the material into the U.S. (although NYC would be their desired U.S. target) and France is getting closer to the U.S. London has too many cameras and is becoming effective at stopping bombers. So, Paris is the most likely initial target for a dirty bomb.