Didn't say that. Said that because islands don't move, and they only have 3 carriers, global force projection is difficult, since they only have 3 carriers. We could put 5 carriers over there if needed, and still have 6 others to roam over other places in the world.
Global force projection cannot be done from an island.
As far as subs being the real advantage? If you are talking about our ballistic missile subs, they aren't as much of an advantage as they are a deterrent. If they have to launch their missiles, the whole world is gonna go to shit, because that means nuclear war. Fast attacks work about the same as a destroyer or cruiser, and are good for 1 to 1 or maybe 1 to 3 combat, but they aren't the force multiplier that you might think.