What war? The U.S. is invulnerable to invasion. The only conflicts that the U.S. would possibly need such a massive global military for would be foreign wars to maintain its world dominance (e.g. containing China, proxy wars, etc.), which I contend are pointless and destructive. I disagree with your implicit premise that the U.S. has to be the global hegemon - it does not have to be, especially when the most urgent geopolitical issue is climate change. Who is “top dog” and how their military is going to fuel their tanks doesn’t matter when the entire world is facing environmental catastrophe.
I’m glad our spending levels are apparently as low as they’ve been since the 1930s, but I’m not sure how that is relevant to the U.S. military’s fuel usage and carbon emissions, which are almost certainly higher than in the 1930s.
> the world and our adversaries would take notice, and we don't want the consequences of that
The consequences being, I assume, the end of U.S. hegemony?