American Individualism?

As I experience different areas of the world and of my own city, I am often struck by one similarity that seems to cross every culture except America (and perhaps Western Europe): the ubiquitous mobs of family groups. 

Puerto Ricans, Middle-Easterners, South St. Louis Bosnians- they travel in age-defying herds. Sometimes segregated by sex, sometimes not. To me, it's a wonderful thing to see all the generations loudly and openly interacting- the parents not acting like the children are a burden, the teens not acting like they're too cool, the grandparents shuffling along and realizing they're the most important person around (and the rest of the group acknowledging that reality).

I really don't want to rant about how, despite our frequent shouts about emphasizing the family, we continually deconstruct the family through almost every institution we have- the very fact that we have to 'emphasize family' shows that we don't, indeed, emphasize family- but I just want to know how we got here? These other cultures are our heritage; we were melted together from the hispanics, the Africans, the eastern and western Europeans, the Asians- and all these cultures, for the most part, still expect to see children with parents, grandparents with children, aunts and uncles with everyone else. When did we lose that? Was it the industrial revolution (my personal scapegoat for most of America's ills)? Was it the very act of crossing the ocean, then crossing the prairie, that demanded rugged individualism and a split from the security of family?

There are some good things about us being this way... the boldness to make decisions, despite what our family and friends think, for one. But I believe we lose a lot when we further separate ourselves into generations, as well as ethnicity and economic station.  It's just one more barrier that we build between ourselves and the people around us- which in this case, are our past and our future.