Upon the invasion of France in 1940 by the Germans, Morgan left for the United States and Hollywood where she was contracted to RKO Pictures in 1941. Her career there proved rather disappointing, apart from "Joan of Paris" (1942) opposite Paul Henreid, and "Higher and Higher" (1943) opposite Frank Sinatra. She was tested and strongly considered for the female lead in "Casablanca" but RKO would not release her for the amount of money that Warner Bros. offered. Morgan did work for Warners however in "Passage to Marseille" (1944) with Humphrey Bogart.