I do think they would prefer to have 5-6 go off at once, but the risks of being caught are very high.
One thing about 9-11 that was clear was how simple it was. Bin Laden vetoed a more complex plan becasue it was too risky and he didnt want to get caught.
Sneaking 5-6 bombs over the border one at a time, planting them and waiting for some future opportunity to use them seems very risky with a high degree of being caught.
Better to get one sail into NYC harbour and detonate it.
That is probably true. If there are six bombs being smuggled separately and one is intercepted, the country would turn itself inside out to find any more. The effort would be extreme, to say the least.
You could certainly be right.
I do suspect the future will unfold differently than you expect.
Actually, I wouldn't be surprised if they tried hard and succeeded at least partially in coordinating lots of mayhem around the globe at the same time they lite off nukes in the USA.