So, if the decline has been going on since the 1970s and if the US became an empire after WWII, then we have not quite 30 years of empire followed by 40+ years of decline. I think I agree with Carrol here. It is probably not right to think about it in terms of rise and decline. But even if one thinks of it that way, I am sure many in the global south would agree that the US's impact declined in the 1980s and 1990s. This then poses the question of weather it isn't exactly what we, as leftists, would want: US imperial decline that is. Rather then fall into that type of either- US domestic prosperity- or - some sort of chance for improvement in the lives of those in the south- it is better to think about how the very peak, booming years of US empire were premised on the utter abuse of those not lucky enough to have been born here/there. If so, then we must also view the peak, boom years of US empire in retrospect as not really something to long for nostalgically. However, all of the above is clearly too zero-sum in nature. Better to focus on the impacts of both periods (or alternatively the continuum of changes in capitalist imperialism) on working people everywhere. Doing so reveals the problems during both eras and points out clearly that the there is no easy answer, nor do our problems vanish in some past that never really was, US decline or not.
Brad