Nuclear attacks via slow overseas container ships are a very dicey, very unlikely situation. Doable, but extremely unlikely due to the technical support that nukes require.
The half life of the atomic trigger isotopes is typically less than 90 days. Likewise, the radiation from the atomic core and shell plays havoc with the electronics and conventional explosives used to start the chain reaction. Moreover, heavy metals such as uranium and plutonium are among the most rust-prone, fragile metals known to man...not a great thing to have working against you if you are trying to ship a working device overseas...and the assembly of such devices on-site requires extremely competent personnel and a clean lab...something that takes a fair amount of effort to put onto an ocean going seasick machine for an 8 to 12 week journey.
And such an attack would only work once. All ships would be halted miles off of our coasts after the first successful blast.
As for a bio attack...bio agents are piss poor military weapons. They make for great terror weapons because they frighten the effeminate liberal news media...but they don't kill on the spot and can be contained and fought with medical technology.
The transit time for a container ship across the Pacific is less than ten days.
And such an attack would only work once. All ships would be halted miles off of our coasts after the first successful blast.
The Chinese have a missile laucncher that fits into a container. No such luck. They could deliver a good many missiles that way and our SDI system would be worthless.
As for a bio attack...bio agents are piss poor military weapons.
But very effective for causing domestic panic, as I said. So far, all you've done is reinforce my point.