With the end of World War II, the United States became a world superpower. Its strength and status reached another peak in the mid and late 1990s as the Cold War ended: it accounted for about 30 percent of global economic output. However, after it entered a new economic cycle from 2000 to 2001, the American share of the world economy has gradually dropped. But the United States is still the only comprehensive superpower in the world. The difficulties and problems existing in the United States currently are fundamental or comprehensive. Some may be short-term. No overall, obvious and fundamental “decline” has appeared in the strength and status of the United States yet. Although the strength and influence of the United States is somewhat less than it was before the economic crisis began in 2008, no clear long-term decline trend has appeared.