I lived in big cities for all my life with short trips to the country in summer, from my experience is that those who live in the city men would shake hands and/or nod, rarely hug. The ones that live in smaller towns/villages tend to hug a lot more.

With women it is if you are an acquaintance then a nod, a friend usually a hug, can be a kiss on the cheek sometimes. With women from smaller towns they might hug and kiss strangers probably out of habit.

Since US is quite rural that would explain more hug prone culture.