P.N.
I think it's a Western thing, not just US. And the interventions begin with the the births themselves. I think one of the biggest interventions that causes issues is the idea that early independence is a good thing. Babies were meant to be dependent on us. They were meant to be within reach at all times, or better yet, attached to us, and meant to nurse on demand 24 hours a day (it's biologically normative for them and us). Everybody's obsession with sleeping through the night asap drives me crazy. I get it, we need sleep too, but really babyhood is such a short time. I think if we try to remember they are supposed to be dependent and listen to our instincts rather than others it can go a long way to supporting nursing-friendly practices.
There was a great article in Mothering a few months ago (maybe Aug or Sept?) written by a Canadian woman living in Mongolia about their breastfeeding culture. Breastfeeding is highly valued, babies are nursed every time they make a peep and no one thinks it's weird no matter how long someone is nursed. There is no weird stigma attached, no one has issues about it. You should check it out.
I'd recommend, as others did, any Dr. Sears book. I'd also recommend finding other moms who are like minded through LLL or API meetings or whatever. If you are surrounded by people who think breastfeeding is normal, it is easier to get beyond all the negativity from others.