二十世紀之初，美國疆域已定，以嶄新姿態進入強權政治籠罩下的國際社會。其時 歐洲列強在全球掠奪殖民地，各據一方的勢力圈至此已大勢底定。得天獨厚的美國固無展領 土之野心，但亦不能忘情於其在遠東的經濟利益。中國的地大（天然資源）、人眾（廣大市 場），自然地成為她對外關係的興趣焦點，當時積弱不振的大清帝國在短短半世紀內，已把 中國弄得支離破碎。在「天賦使命」（Manifest Destiny）的自許及現實的利益下，美國宣 佈了她「門戶開放」的對華政策。但初生之虎畢竟先天條件有限，眼見帝國主義者在中國之 燒殺掠奪（如甲午之後日本在旅大的泯滅人性的行為）只得無奈地把威爾遜總統的崇高理想 束之高閣。及至日本軍國主義者強佔了東北，建立偽滿政權乃不得不祭出「史汀生主義」。 這是美國軟弱無力，理想與實踐前後矛盾的最高表現。 迨二次世界大戰結束，兩雄並立的世界格局，再度顯示出美國舉棋不定，言行矛盾的外 交政策，一方面竭力反共圍堵，另方面又派遣馬歇爾調停中國內戰。乃至國民黨潰退到臺灣 ，美國落井下石地「待塵埃落定」，發表了對華白皮書，在在都顯示出美國無意使用其國力 來強化其宣示的外交政策，美國對華半世紀的政策失敗，大大地淡化了她在國際政治上的領 導地位。

　　　　　The rise of the People's Republic of China as a superpower has imposed serious challenges to the U.S. aspirations in international affairs. During the past decades, the U.S. adopted in three different occasions incoherent policies--the dispatch of Open Door Notes, the Proclaimation of Non-recognition Doctrine, and the Mediation of Chinese Civil War-resulting in serious consequences. Its impact can still be felt today. In fact, America's indecisiveness and incoherence in conducting her relations with other countries have too often led her allies into disillusionment and tarnished her image as a leader. The U.S. has too often declared a policy, then, makes no attempt to enforce them by application of national power. The success of a foreign policy does not come out of vacumn. It entails good timing, sensitive to the temper of international community particularly in an em of "Global Villege." Furthermore, it is deeply conditioned by the reactions of nations with vital interests relative to the issue involved. In the case of Sino-American relations, it should be noted that the interests of the Soviet Union(now called Russia) should always be taken into consideration. Soviet Russia's interest in the Far East has been long and enduring and has been playing a crucial role in Far Eastern international politics. Its position in Far Eastern internation affairs will be an important element even though the Soviet empire is now disintegrated.