The US may no longer be the land of opportunity, but it has been the source of a lot of opportunity. Don't get me wrong, the US has not been the lone source of innovation in the world. But for everything bad associated with "free market" ideology, off-shoring, tax shelters, etc., there is an American notion of freedom underlying internationalization. There have been moments of backlash, greed, and economic setbacks, but in general, the US has championed economic development and cooperation.
It's not always pretty or altruistic, but give people a foothold in the global economy and their quality of life, rights, and social mobility improve. Improvement has been slow in China and Russia, but there has been positive change. Africa doesn't need military intervention, charities, documentaries, whatever... they need sustainable industries. Foreign companies strip mining or pumping oil will never foster a middle class, technology, manufacturing, or research will.