As the leading power in the world, the US has had the most important influence on international society in the 20th century which was named by some as the American Century. The reasons behind the success of the US could be characterized as “4 outstanding”. The first was the outstanding secure environment the US faced when it was emerging. Benefitting from the protection of the Pacific and Atlantic, the US grew to be a world power peacefully and quickly. The second was the outstanding historic opportunity the US experienced when it extended its strength toward the western states. Due to the prevailing attitudes of that time, no European countries criticized the violence and acts of aggression the US committed, which would seem impossible tod...