Three things we must do as a country:
1- Secure the borders, including nuclear detection.
2- Deport known AQ sympathizers, monitor suspected ones.
3- Publicly state the nuclear retribution that will come if such a plan is carried out. Make sure they know that WE WILL DO IT.
That retribution must be against targets these muslims hold dear; Mecca, Medina, Qom, and the capitals of the states aiding the jihad: Riyadh, Tehran, and Damascus! Otherwise they won't care.