The USA idealizes (probably fair to say fetishizes) motherhood. Mothers are wonderful people, sacrificing, struggling, admired, lauded - every bloody thing except supported by maternity leave and fair employment laws! From the announcement to the baby shower onwards people are thrilled for you that you're pregnant - I've just had our second and DH's work colleagues, (whom I know and like but we don't go out to dinner together) sent TWO CAR BOOTFULS of presents home 'for the baby' - even though they all know it's our second, and we really don't need anything (you only really have one 'shower' and that's for your first). They are just so excited and pleased someone's had a baby. My cynical side would say that it's because America is oddly prudish about female sexuality, they have a real madonna/whore complex, as a nation, and mothers are firmly on the 'madonna' side! Still, I benefit from it - people are always leaning into the pushchair to coo, chatting to me in lifts about my lovely baby etc - it's absolutely sweet. Until my toddler starts acting up, of course! :)
An extension of that, I think, is that on a personal level I've never met anyone who wasn't extremely supportive of breastfeeding - would I like a cushion, did I need a drink - and while I hear horror stories about people ordered out of restaurants or shops for bfing, it's the polar opposite of what I've encountered in 2+ years of feeding everywhere.
Sometimes I wonder if it's because there's a strong immigrant/peasant tradition here, and the scramble to be middle-class that involved using formula in the 60-80s in Britain didn't do it the same way over here? But then, their birth process is highly medicalized (everyone sees an OB-GYN and has a baby in the hospital) .. oh, I don't know! Everyone's Irish/Italian grandma breastfed over here, and most women do for at least the first 6-12 weeks. Many then switch to formula, but many also pump. I was lucky to work somewhere that had designated lactation rooms, with fridges, magazines, somewhere to plug your pump, etc. If I were being cynical I would say that lactation/pumping support is a damn sight cheaper and easier for companies than maternity leave, but it DOES work.
Also, I think the internet makes a difference. My mum didn't breastfeed, few of her friends did, and she had no idea that, for example, cluster-feeds happened. My sister and sisters-in-law all did and so gave me useful and supportive advice, and then I had people like tiktok helping me out, even just by reassuring me 'this IS normal!' on the MN feeding boards.
And when I was looking for a doctor for my children (rather than a GP, they go to a pediatrician), I searched online for one that the local LLL called breastfeeding-knowledgeable and breastfeeding supportive. And he really is - lovely chap, his wife fed theirs for ages, was able to diagnose breast thrush etc. Which my UK GP couldn't do. But the internet gave me that power to find out, which my mother's generation just didn't have. They all did what the doctor said, automatically.