I have to say it’s exactly the opposite. There’s no realistic conventional deterrent we could deploy that would be more than a bump in the road. On the other hand, a couple KSS-3 subs off each coast with several nuclear tipped ballistic missiles puts tens of millions of lives and trillions of dollars of infrastructure on the table. It’s about making invasion unthinkable, not desperately fighting an asymmetrical conventional battle we’re doomed to lose.