This societal passiveness isn't accidental: it has been deliberately engineered in North America. The documentary "The Century of the Self" breaks this down better than anything else I've seen/read. There is also, within activist circles, the belief in a mythical version of history in which pacifism, isolated from militance, is what catalyzed change in the past.

Regarding the self-interest of the young, it's a rational thing. If young people today weren't saying "where's mine" then they'd be stupid. During the baby boom there were decent jobs because globalization hadn't happened yet and corporations still had to rely on domestic labor. Reliance on domestic labor also means the elite values having decent public institutions, which strengthen the labor force. Now not only do we have globalization but also systematic looting. Young people get to look forward to having it significantly worse economic prospects than their parents.