Simply possessing Nuclear Weapons buys a whole lot of Deterrence.
Assume the following:
Given these conditions, do you see any country attacking us?
Honestly? Any at all?
You are asking the military question: "What are the risks of a totally conus (continental U.S.) based military with the exception of naval power on the open seas?"
1. Annihilation if an adversary also develops nuclear or other weapons of mass destruction. Mutual destruction is no solace to me. It's still destruction. Were an enemy to gain a technological or strategic edge, then first strike risks increase. Our presence in other countries enables us to deter through influence and intrigue.
2. Economic disruption.
3. Operations other than open warfare....espionage, industrial espionage, computer attack, civil destabilization, etc.
All of these are enhanced by armies of influence and agents of influence/intrigue on the ground in other locations of the world.
My .05 worth, for what it's worth.
I agree in so many other areas. My disagreements in areas other than defense are more questions on new procedures than they are disagreements with the ideas.
For example, you have Medicare becoming a state program instead of a federal program. Why not get government entirely out of the business EXCEPT FOR QUALITY CONTROL LAWS to see what happens in the market place when providers have to deal directly with consumers.