Monogamy is not America's norm. It's been a norm in the making for the past millenia.
Here to quote from a book how monogamy was developed:
QUOTE
What I've discovered by doing my homework is that the moral idea of monogamy (having only one partner at a time) has been formalized, passed down, and force-fed to us culturally by rulers, religions, and women for thousands of years.
I don't mean to get too far out here, but I feel that understanding from where these beliefs came and how they are promoted will liberate many readers.
Onward.
Anywhere from hundreds to thousands of years ago, rulers of lands kept large harems of women. These harems were guarded carefully to prevent any males except the rulers from having access to these women. The penalty for sleeping with one of the ruler's women would be, in an extreme case, your own death and the deaths of everyone in your family and village. (Back then there were bigger risks involved!)
These rulers kept so many women not just for the sexual variety that it provided them, but also for the reproductive power that it gave them. These rulers often had detailed records kept so they could copulate with only the most fertile women and maximize the woman's chance of pregnancy and passing on their own genes.
So what do you think these rulers did to protect their harems?
Right! They passed laws (from which they were exempt) to promote monogamy.
In these times there was a great shortage of women, so these laws would discourage married men (those lucky enough to find a woman) from seeking sex outside of their marriage and therefore further protect the ruler's harem.
Next, we have the church.
Many religions prohibit sex, make sex 'wrong', give it some name with a negative connotation like 'fornication', or in one way or another discourage it.
I once heard a wise man say, "Religions take everything that your DNA naturally wants to do to survive and procreate and make it wrong." Why? Well, if you're busy fighting your internal drives, and you see God as the only way to cleanse yourself of these 'bad' thoughts, then you are a much better SHEEP.
If you want to get people to follow you, first confuse them, then convince them that you know the way to get them out of their confused state. Easy.
Finally, we have women. This is the interesting one.
If you look at it from an 'economic' standpoint, it doesn't benefit women at all to have their man running around having sex with other women. She can only be pregnant with one child at a time, and she can only raise a limited number at a time. So having a man who's out spreading his seed is BAD BAD BAD for business for her.
When you're out spreading seed, you can't be working or at home helping. Even worse, you might have other kids with other women who will further divide your attention and income. (By the way, I'm not saying that there's anything wrong with women's perspectives. I'm just saying that if you look at it from their point of view, there's not a lot of benefit to having a man who likes to sleep with a lot of women.)
So anything that promotes monogamy like religion is seen as 'right' to many women, as it goes along with what they think and feel.