For rather earth shattering global events such as leaving one of the most stable and powerful military alliances the world has ever seen, I'd like a little more than "writing on the wall" as evidence.

Just because they say they need to be more self-reliant doesn't mean they're pulling out of the alliance. Even Trump, with whom I disagree on pretty much everything, isn't leaving the alliance despite his overheated and irresponsible rhetoric. And "quickly becoming unraveled" is not "we want to leave" it's more "there's a maniac in the white house destabilizing everything that has worked for the past half century".

EDIT: Typo