摘要
The power position and influence of a country depend on its comprehensive national power based on economics. While addressing to the press in Kansas on July 6, 1971, President Nixon noted: "Comparing to our overwhelming position at the end of World War II, the United States is now facing immense challenges that we have never expected before. " He added, "In terms of economics, the United States is no longer a dominant power or an overwhelming global power. At present, there exist not only two superpowers. In consideration of eco-