That was the original reasoning for the 3 (now 12) mile territorial water limit, which was how far coastal artillery of the time could reach. The US lobbied fo

That was the original reasoning for the 3 (now 12) mile territorial water limit, which was how far coastal artillery of the time could reach. The US lobbied for extending this repeatedly, and applies a de facto larger limit to the continental US. This makes sense if you consider that modern coastal artillery uses over the horizon radars and missiles. But a reasonable argument can be made that contemporary coastal defense is not artillery, but air-launched missiles whose range can be considered to be the missile range plus the combat range of the launching aircraft.