Well, interesting that you chose the USN for your example, because basically the mission of the Navy is to be a blue water one: to be deployed not just overseas, but on the high seas.
I'm talking Air Forces bases overseas. Army bases overseas. Engaging in "limited" armed conflicts or "peace keeping missions." Etc.
OK if the Navy is only "blue water" - what are they supposed to be doing out there? Does the survival of the nation depend on them? Hard to say. I don't expect China will defend our commerce - but is that the survival of the nation?
As for bases overseas, I guess I have to look at history. Did the survival of our nation absolutely depend on securing Europe and Japan after WWII? Maybe not except any logical person would have assumed the Soviets would have just taken the entire continent. A threat to us? Maybe not but I'm not sure I'd want to find out. I think each one of the "limited" or "peace-keeping" missions has to be evaluated independently. I'm just not ready to say NO to any of them or Yes to all of them. Too many grays.