http://en.m.wikipedia.org/wiki/National_trauma
A national trauma is a crisis or a tragic experience which affects the spirit of a nation or an ethnicity, sometimes for generations to come. Large-scale disasters like war or genocide inevitably have this effect, but in an otherwise stable and prosperous country even a specific event (like an assassination of the leader or a transport disaster) can be traumatic.
Germany: Treaty of Versailles, defeat in World War II, Berlin Wall
Ireland: Great Famine
Israel: Holocaust, Assassination of Yitzhak Rabin
Japan: Black Ships, Atomic bombings of Hiroshima and Nagasaki
United States: American Civil War, Assassination of Abraham Lincoln, Assassination of John F. Kennedy, Vietnam War, September 11, 2001 attacks
Netherlands: The loss of the 1974 FIFA World Cup final against Germany, as well as the loss of the 1978 FIFA World Cup Final against Argentina and the loss of the 2010 FIFA World Cup Final against Spain
Sounds about right.