It influenced the U.S. into giving official support to the Allies even when it was not directly involved in the war.
The reason for this is that the atlantic charter was an agreement between the United States and the United Kingdom (hence the name) in which both countries laid out ther vision for the future of the world: a world where liberal democracy dominated and economic freedom dominated, a view that was obviously contrary to the views of both Nazi Germany, Fascist Italy, and the Soviet Union.
