Werner Herzog’s films tend to thrust man up against nature, and nature is not a particularly forgiving adversary. His latest film, “Rescue Dawn” (opening Wednesday), revisits these themes as it follows the ordeal of the German-American pilot Dieter Dengler in the jungles of Laos after he is shot down by the Vietcong in 1966 during a secret bombing raid. “Rescue Dawn,” the first screenplay Mr. Herzog has written in English, is in many ways a mash note to America. Mekado Murphy reports….