Armed with a two-megaton nuclear warhead, What will happen if Russia uses Poseidon torpedoes

The latest announcement means that Russia will soon possess a new deterrence weapon that, if used, could cause devastating damage to coastal cities in the US. Armed with a two-megaton nuclear warhead, the Poseidon if used, could cause devastating damage to coastal cities in the US. can destroy aircraft carrier strike groups and enemy infrastructural facilities in coastal regions.