There's quite a few posters on this thread who seem remarkably not fluent in English/American English on this thread.
The US did very nicely out of WWII. No buildings to rebuild. No years and years of rationing after VE Day and VJ Day for them. The Golden Age of Capitalism.
From the Library of Congress:-
When World War II ended, the United States was in better economic condition than any other country in the world. Even the 300,000 combat deaths suffered by Americans paled in comparison to any other major belligerent.
Building on the economic base left after the war, American society became more affluent in the postwar years than most Americans could have imagined in their wildest dreams before or during the war. Public policy, like the so-called GI Bill of Rights passed in 1944, provided money for veterans to attend college, to purchase homes, and to buy farms. The overall impact of such public policies was almost incalculable, but it certainly aided returning veterans to better themselves and to begin forming families and having children in unprecedented numbers.