China has access to vast resources of poverty stricken laborers. Lacking most of the basic quality of life safeguards that the US has in place, it is able to put children into factories instead of schools and bolster its workforce even further. Once upon a time, you bought American if you wanted strength, quality and durable products. This is no longer true in the grand scheme of things. America has become far more concerned with how quickly we can produce how many units for sale, putting us into the same arena as China with half as many workers.
The U.S. may be the world's biggest economy today, but it won't be for long. That is, if it hasn't already been surpassed by China. The U.S. has long since ceased making things and now only buys thing -- oftentimes from China. The trade imbalance has become so lopsided that I wonder what we would do if China stopped doing business with us.
China's economy has grown in leaps and bounds over the last several years, but only because it's so adept at producing cheap consumer products for sale at U.S. outlets like Walmart. The reason it's so adept at manufacturing and therefore seems to have an advantage in international trade is because the people there enjoy a terrible quality of life. They aren't free to participate in the economy there in a way that would lead to the kind of growth that's made the U.S. such an economic superpower.