I think we would be fine with a smaller military. Nobody is talking about completely stopping military expenditures. The question is whether it really needs to be as big as it is right now.
Overturning so many regimes in petrol filled countries is a messy business. I think a big chunk of the spending goes to intelligence and misinformation.
Personally I think a big chunk goes to not well thought out missions like Syria, Afghanistan or Iraq. It seems nobody is willing to admit that there is no path to winning or ending things so they just keep going and spending a lot of money and energy. And the defense contractors are certainly happy with this.