As I pointed out in my earlier post, had the Nazis been allowed to complete their conquest of Eurasia, and it was a very near thing, they could within 7-10 years have brought overwhelming military power to bear on the US, their only potential remaining foe. That could have led to the end of the US.
In this scenario, who got the A-bomb first would have been crucial.
Of course, from the mid-50s on Soviet H-bombs could have destroyed the US pretty completely in a few hours.
Are you seriously trying to equate these military threats with that posed by a few tens of thousands (at most) rag-tag terrorists who can't even manufacture their own weapons?
Can they do a lot of damage? Absolutely!
Can they conquer and occupy us, or destroy us? No way!