Not that you're exactly wrong, but I would argue that advantage meant more, not less, as time went on. In both World Wars it granted the US mainland the insuper

Not that you're exactly wrong, but I would argue that advantage meant more, not less, as time went on. In both World Wars it granted the US mainland the insuperable strategic advantage of being effectively impossible to attack in any meaningful way - not so much, though, in the days when the Royal Navy still bestrode the world.