Comment by jltsiren
Defense is a bit like advertising or finance. It has some aspects of a zero-sum game and a negative-sum game. All the money you invest in it is wasted. But if your enemy/competitor chooses to waste more money, you may be in trouble.
From an European perspective, the entire purpose of NATO from 1992 to 2022 was to prevent wasting too much money on defense. Because, for some reason, Americans were willing to do it instead.
Then Russia invaded Ukraine, and the calculus changed. Now European countries are rebuilding their defensive capabilities, while Russia is still bogged down in Ukraine. Given the lack of credible short-term threats, limiting defense spending was clearly the right choice until 2022.
Also it makes sense to have a capability only once within an alliance. If the US has the command, space and air capabilities, why would anyone else need to have this. You can add to their capability by buying F-35s and hosting their air bases.
Now that we are not allies anymore we need to wastefully build up our own command, space and air capabilties resulting in duplicated effort.