Since the middle of the 20th century, most Americans have grown comfortable with the world view of United States as the dominant economic and military power. But with China rapidly joining the modern world, that conventional view will have to change. And adjusting to that new reality will be a challenge for U.S. policy makers as well as average citizens.

With 1.2 billion people in a rapidly developing economy, China is already a major economic force as the source of manufacturing for many of the goods consumed by Americans. The full scope and magnitude of China's economic power was revealed in a report issued this month by the Earth Policy Institute that showed that China has already surpassed the United States in consumption of just about every food and industrial product. Chinese consumers buy more refrigerators, televisions and cell phones. The one area where China still lags the United States is in cars and oil. But as the Chinese economy continues to grow and more of its billion or so citizens climb into the middle class so that they both desire and can afford a car, that statistic will surely swing toward Asia also.

China already consumes more steel than any other nation in the world, which has contributed to rapidly rising prices for steel and even scrap metal in the United States and Europe. Higher prices for steel have been good for U.S. steel manufacturers, but will not be so good for U.S. consumers, who will have to pay for that higher-priced steel in prices of the finished goods they buy.

Of more strategic, economic, political - and possibly military - significance is the coming impact of China on the global supply of oil. In what some analysts are describing as the coming war for resources, China will be consuming more and more oil, making it harder for Americans to consume at current levels - or at current prices.

This troubling scenario should strengthen the argument for the U.S. to press harder for greater fuel efficiency from manufacturers of cars and trucks, and to eventually develop alternative fuels that will make this country less vulnerable to China's soon-to-be-insatiable appetite for oil.

China's current appetite for cars still pales when compared to the United States' - 24 million to 226 million - but accelerating living standards in a nation of 1.2 billion people will clearly push China well ahead of the U.S. in the numbers of cars on the road.

Again, this might turn out to be a lucrative market for GM or Ford, but the increased demand for oil and resulting air pollution will fuel other, less attractive, issues.

The rapid economic growth in China poses many challenges to the U.S. economy and U.S. political leaders - as well as the global environment.

As if those challenges were not enough, U.S. Senate's Armed Services Committee recently held hearings about intelligence projections that suggest the size of the Chinese naval fleet could surpass the U.S. Navy within 10 years. That is a chilling prospect, and something with which U.S. political leaders as well as average citizens will have to grapple.

Just how the world will change as China marches toward greater dominance and influence is not known. But the new global dynamics probably mean an end "the American Century," and difficult adjustments from Main Street to Pennsylvania Avenue.