Worth pointing out the author of the piece, Stephen Bryen, is a Senior Fellow at the American Foreign Policy Council (Source : https://www.usnews.com/topics/author/stephen-bryen ). This organization (https://en.wikipedia.org/wiki/American_Foreign_Policy_Counci...) seems to have sided with some of the driving forces behind the US-led invasion/occupation of Iraq/Afghanistan. This doesn't invalidate the analysis necessarily, but it feels like this article is coming from someone in an organization that potentially falls in the particularly hawkish part of the policy spectrum.
This author is just trying to lobby for buying/selling weapon. I don't see why we should give this article any eyeballs.
Also, the best deterrent is not a good defense system that this guy is trying to sell. It's the threat of 100 nukes erasing 50 cities of the invading country. That threat is real, and that's the US best defense at the moment.
That sort of reasoning (MAD) works great against Russia during the cold war.
It is less robust once you factor in rogue and non-rational adversaries. I'm no saying you're wrong, but the risk from these actors isn't truly mitigated even by having overwhelming conventional and non-conventional weapons, second-strike capabilities (or anything really_.