That fellow and his movement would be as much symptoms as causes, of course. Ash had Obama or Obama's America ca. 2013 in view when he coined the term "withdrawalism." A consistent withdrawalist might would be constrained from acting to preserve or enhance the value of NATO, and a rigorously consistent one would be constrained even from acknowledging the question or from looking into it.
All that said, I readily acknowledge a counterargument, which is also a complementary view. I even went on to tweet a short summary. I think I'll tweet-drizzle it.