I don't believe they are separable as you do. If we decide to turn our backs on the world militarily, we certainly do so with the knowledge we cannot protect our interests around the world. In that event we wouldn't have many companies that would care to risk billions of dollars of investment money overseas. We would be loathe to set up trade agreements. We would withdraw.
I'm not against the idea, per se, but realistically I don't think you can withdraw the military and maintain the economic aspects.