"Nuclear Submarines" doesn't mean anything.
They could be nuclear powered Hunter Killers, Cruise missile launching, or carrying ICBMs.
Moving them "closer to Russia" means nothing either as ICBM's can hit the Russian interior from practically anywhere on the globe, and the USN stations HK's on watch outside Russia's major Arctic and Pacific ports as a matter of course anyway.
It's a meaningless soundbite being amped up as something significant for the sake of producing copy.