Not every rocket - liquid fuel ones only to a very limited, logistically awkward and costly degree. As the US and Soviets learned, keeping fleets of liquid fueled ICBMs ready to go is dangerous and expensive. Storable fully solid fuel ICBMs such as current-generation US/Russian stuff are quite different.

> each from 400 undisclosed locations

A point of clarification, submarines are the only nuclear platform with "undisclosed locations." It is trivial for a nation-state to observe the construction and fitment of a fixed ICBM placement, or track the movements of a truck/rail mounted launcher.

It is certainly not trivial, and definitely out of reach of most nation states out there.

I'm sure U.S. at least tries to keep track of Russian mobile launchers, but to which degree it is successful we wouldn't know for sure. And pretty certain Russia would have problems live tracking launch vehicles (if the USA had any).

What prevents the usage of decoy trucks?