It seems clear that globalisation has coincided with and probably caused increased inequality within the US, but has it decreased inequality within the global system - i.e. by enabling China/India and their workers to move up the food chain?  

It isn't workers that benefit from this the most.

Remember that while the relative distance between China and India and the developing world is closing, inside of India and China, inequality between rich and poor is rapidly increasing.  I know more about China than India.  To give an example in 1980, China's gini coefficient was in the 20s, it was similar to the Scandinavian countries.  Now it's in the upper 40s, and it approaching Latin American levels.   India, I don't have stats for.

So what we are witnessing is the growth of inequality within nations, at the same time that inequality between them is shrinking.  (And don't forget that Africa is falling ever further behind.)

So there is no birth of a global middle class.  Instead there is the segregation of the world into rich and poor.  The difference is that this class system is no longer quite so color coded......

And I'll give my consent to any government that does not deny a man a living wage-Billy Bragg