If al-Qaeda had nuclear weapons here in the United States they would have used them already.
You said -- "If al-Qaeda had nuclear weapons here in the United States they would have used them already."
Have you read how many people have already said that?
They might not be ready to use them yet. Perhaps they are putting the finishing work on it right now. Perhaps they are waiting for some particular timing, just like they did with 9/11.
And perhaps they are not here yet -- but are getting things together and will be here soon.
So, what you say doesn't work or fit.
Regards,
Star Traveler