I don't understand the long term strategy in such a move.Nuclear propulsion is not against the NPT.
However, this does set a precedent for a non-nuclear power and opens the doors for other major players like Japan and S. Korea (and even Canada) to go nuclear with their submarines.
Nuclear proliferation will inherently nullify any advantage in US conventional military dominance.
When one day US is no longer the top dog, there will be even less incentives for vassals to hang around if they have a stealth deterrent lurking about.
Is this alliance sustained by rational risk mitigation or blind racial pride?
What will happen one day when US population is predominantly Catholic Latinos?