Is western prosperity dependent on immiseration of the global south? No, western prosperity depended on the upward pressure on wages supplied by the big socialist examples. You could argue that it was precisely that a big portion of what would have been the 'Third World' was mostly not in the capitalist orbit that most signally contributed to the development of the west post WWII. High public spending, high manufacturing wages, strong unions, etc. Immiseration in the U.S., on the other hand, is dependent upon suppression of the third world, the second world, and everyone else.
BTW, what's the origin of the 1st, 2nd, 3rd world division?
Jenny Brown