Russia, and probably China as well, could hit the U.S. with a sub launched ballistic missile from their own waters. Why would they come to the U.S. coast to fire one? And if it was a missile where did it land?
Response time. The closer you get the more likely you hit your target before they can shoot back.
>>Why would they come to the U.S. coast to fire one?<<
For the same reason we would. Delivery time. A sub launched missile can thwart missile defenses and hit targets within minutes without going sub orbital.
Launching thousands of miles from a target, the missile needs to reach a sub orbital state and utilize the rotation/curvature of the earth to shorten delivery time. Sub launch...not so much.
Two words depressed trajectory.
Not only is it much faster than a ballistic trajectory the response window for exo and especially endo atmospheric interceptors is drastically reduced. With MARV warheads it’s effectively impossible to intercept a mach 12 MARV that is pulling 100+ G turns in the 30 seconds or so it’s above the radar horizon inbound.
The USA tested the MK500 evador warheads package in the trident right before the cold war ended it was viewed as such a capable first strike weapon it was never fielded since its sole purpose was first strike against hardened targets with a CEP measured in tens of meters which puts even a 5000 psi silo inside the fireball where even concrete is vaporized by the 100+ million Celsius thermonuclear fireball.
https://scienceandglobalsecurity.org/archive/sgs03gronlund.pdf