It's pretty accurate if you consider immigration overall, and for one simple reason: US has the most extensive family immigration eligibility, at least among developed countries. In Canada, for example, you can't sponsor your grandparents for permanent residence; but in US, you can. This is also why US is the only developed country dominated by family rather than skilled immigration, by the way.
I stand corrected wrt this particular category and Canada. It's not the case for most other countries, though. And it is still the case that more family members are eligible in US than most other places. That US has a lot more family immigration compared to others is also an objective fact.
