While Poirot is Belgian, Christie herself was born in England in 1890 to an American father and English mother (source).
Murder on the Orient Express was loosely based on the real-life kidnapping and murder of famous aviator Charles Lindbergh's young son in 1932. The case captivated and outraged the American public (source).
Agatha Christie volunteered as a nurse for the Red Cross during World War I (source).
Christie was a regular passenger on the real-life Simplon-Orient-Express and was even once stuck on the train for six days because of snow (source).
Hercule Poirot appears in 33 of Christie's novels and 54 of her short stories (source).