He's talking about in comparison to the rest of the world, which doesn't mean shit because the third world is most impacted by the exploitation of capitalists, the middle classes in America are impacted to a lesser extent, still they're exploited and the 1% pigfucks in murica are leeching hoarders of undeserved wealth.
What do you mean it doesn't mean shit? It means middle-class Americans are dependent on imperialism to sustain their standard of living. Within the US there is a class conflict between these middle class petit-bourgeoisie and the big bourgeois capitalists, but globally their interests converge more than they diverge. A quick illustration of this dynamic can be seen in the way that middle-class America generally has no solidarity with victims of imperialism whatsoever and does not see imperialism as something wrong in and of itself, and in fact sees it as desirable and right and just. Anti-imperial sentiment only appears in the middle class when it is perceived that imperialism is serving the interests of the big bourgeoisie at the expense of the middle classes (i.e. "Stop sending our boys off to die in pointless wars for oil"). They are almost wholly reactionary in character which is to be expected considering their class position, they cannot be expected to be allies in any sort of revolutionary situation. In fact the petit-bourgeoisie who are frustrated by the political dominance of big capital often tend to form the nucleus of fascist movements.
Middle-class Americans (and middle-class Westerners generally) are exploited relative to the global capitalist elites, but relative to the rest of the world they are in fact some of the greatest beneficiaries of the Global Capitalist Holocaust Slave Empire, and most of them have no interest in seeing that system come to an end.