Based on what my American friends told me, I think it was only a couple of generations of Americans where that was true. Before that, Americans too had stronger familial bonds. No first hand knowledge though.
If you're in your 20s-30s, best case your grandparents grew up in the 1950s-60s - which absolutely wasn't a walk in the park, but the average American was miles away the richest person on the planet back then, and the "nuclear" family was the structure of choice (that's why it's called the nuclear family - 1950s techno-optimism a la Fallout)
On the other hand, if your family immigrated then the familial ties based system continued to exist.
