This article examines the hypothesis that although the level of democracy in a society is a complex phenomenon involving many antecedents, consanguinity (marriage and subsequent mating between second cousins or closer relatives) is an important though often overlooked predictor of it. ... The data suggest that where consanguineous kinship networks are numerically predominant and have been made to share a common statehood, democracy is unlikely to develop.This is an advantage of the American family. America has very low rates of cousin marriage. Many other countries have high cousin marriage rates, and they are divided into clans that make democracy difficult.
It is too simplistic to look at whether a culture is pro-marriage, or pro-family. Some have family values that contribute to American ideals, and some do not.