Arguably, what makes any economy strong is labor, and manufacturing. The US has shifted from a manufacturing base economy to a financial / service based economy. Corporations are making profits, but not creating anything. By giving China and other countries jobs, it's given them economic power. An anti-labor trend that began in the 1980's has eroded the labor class in the US to the point that even with increased productivity, wages are flat or declining. But this isn't an argument about capitalism; Germany has maintained a trade surplus, competing with the same global market forces the US is, but has retained it's best quality workers with high pay and benefits in Germany (although there are factories all over the world). The German model proves that it is possible to run an economy with the pressures of globalization without off shoring workers, and that manufacturing is not dead.
The important thing to remember is that it didn't have to be like this. The historical trend was not the result of some sort of natural economic law but of decisions made and policies taken. The economic elite tell us that this is the result of technological progress, globalization, etc., etc., but those very things could have led to better lives for the majority of people if different policies were followed. But that would only happen in a world where the leaders have the best interests of all at heart and we don't live in such a world.
One interesting correlation (perhaps coincidence) 1974 was the first year since WW2 that wages of the American worker declined. This was 3 years after the Nixon Shock, when the value of the US Dollar began a significant devaluation (decline), ending up being down 80% against the Swiss Franc as of today (2013).