Because with a cruiser, you have to integrate all those weapons, sensors, computers and such, as well as building it to military standards (i.e. so it can take some level of damage) that the nuclear icebreaker comes with.
As for submarine, often metal alloys different from that of surface ships are used in the hull, for starters.
The integration has no business at all with the civilian shipbuilding.
And generally, the characteristics that you mention doesn't affect the capability of the warship to sail, participate training and launch missiles against inferior enemy.
So, we don't know even if the USA is capable to do the above stuff.
All that we know is from the three NATO warship collision one sunk , and two survived with loss of main sensor and weapon systems, and with need of main repair at manufacturer site ( means in wartime they would be considered as total write off, because they would use up the space required for manufacturing of new warships)
The Ford , littoral combat ship, zumwalt are not reached the level described by you.
So, by your definition Russia should be able to pump out warships in unlimited number.