In the 90's America was in an amazing stretch of super prosperity, there was largely peace around the world, we mostly liked our government and everything was roses. So we listened to grunge and emo and nine inch nails and metallica and all the rich white kids whined about how hard life was.
I guess if you look back at the first age of disco, which started around 1970, it was another really down time for the US. I'm sure someone else could fill in the gaps better, but a few things are obvious. It was near the peak of disillusionment with the Vietnam war (Tet was 1968, we were in 'nam roughly 65-73). Watergate was 1972 so there was much hate and distrust of government. We weren't too far off the Kennedy assasination and the Cuban missile crisis still, so there was fear of the cold war and all that. It was also a period of severe racial strife and unrest among the poor; it was the time of massive urban riots all over the US, mainly 67-69. From that you obviously get the most candy pop music fad ever, with a glorification of living fast and partying hard.
It will be kind of a shame if Obama wins and makes the country happy again, because the whole current youth movement of partying and sex and fast living will die. Fortunately, I'm quite sure that even if Obama wins the US is still headed for the shitter, so the fun new-disco is here to stay for a little while.