WWII bunker "Battery 223", Cape May, NJ

I think the Americans may have been expecting battleships attacking the coast with cannons. Radar was not usable until several years later, so a battleship could remain far enough offshore to be unseen. Also, a shore invasion might have been expected. This area is sparsely populated even now, so might have been a good place for troops to land. In any case, no invasion was attempted on the east coast of North America, so perhaps the Americans were defending against the wrong enemy.