United States was the global manufacturer and supplier for the Allied powers during both of the world wars. Their involvment played a vital role in winning the war against the agresors. Their goal was to restore the balance of powers in Europe throughout both of the conflicts. This served as a point of critisism, advocation US's goal of restoring Germany after it's anialation after WWII, in order to create a counter-balance for the upcoming threat of Communism from the Soviet Union. The failure of United States to join an international organization LON (League of Nations) may have been the reason for it's failure to prevent another conflict.
As for the WWII peace negotiations, the Allied powers nearly publicly proclaimed the importance of US's invlovment in the new international organization for peace - United Nations. Their headquaters are currently located in NYC near the Hudson river, which is extremely expencive land donated by the Rockefeller foundation.
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