Andrew Cherlin contrasts U.S. and European approaches to marriage. One strong finding is that the U.S. is much more concerned about marriage, while the Europeans have more regulations on reproduction.
The intense debates that we have about the nature of marriage, including homosexual marriage and polygamy, are just not repeated with the same intensity in Europe. Many European nations have adopted same-sex marriage or civil union laws. Indeed, their civil union laws have turned into a whole "marriage lite" category that is mostly used by heterosexuals. Polygamists have begun to use European civil union laws to validate their unions, as well.
On the other hand, European law is more oriented toward children. Many European countries provide money for child expenses, day care, and maternity and paternity leave - a fact often mentioned in U.S. family policy debates. What is less well known is that most European legal codes are much more restrictive than American law about "assisted reproductive technology" - sperm banks, in vitro fertilization, and the whole panoply of high-tech baby making. American states, by constrast, regulate the fertility industry very lightly. There is not likely to be a European "octomom."
I read this difference a little differently than Cherlin does. I think we emphasize marriage because it is the most reliable, most individualized, and most portable institution for raising children. The more parents raise kids, the less society has to. Europeans, on the other hand, rely on the state more for many functions, including quite a bit of child rearing. Thus, the state regulates who can make children more closely, since the state will do more of the raising. But the Europeans care less about who marries whom because they don't rely on married couples to do most of the raising of the next generation - if there is one.