We don't need to make exact replicas of every single old material. "Won't have an effective arsenal within a century" is silly.

And that absolutely was not a non-sequitur.

Thermonuclear weapons have considerably tighter engineering requirements than sidewalks. So much so that the comparison is ludicrous.

Even if you think the comparison is very bad, it's not a non-sequitur.

"If Roman cement misconceptions exist then the US hasn't forgotten how to make Fogbank" is literally a non sequitur.