>I would have to question rather strongly the blanket assertion that people in Mexico just fundamentally care more for their families than people in the US do.

No one said that. Societal and cultural conditions being what they are in that part of the world lead to a situation in which living together and pooling resources makes a lot of sense. That's not true for most Americans. It has nothing to do with "caring" more or less. Most people, given the opportunity to do so, will chose to live on their own rather than bunk up with three generations of family members.