I think that there is also no culture in the states of travelling to low to medium cost golf destinations in the USA for holidays and as such carts become a small cost in the big scheme of things.
It's easy to think this if your exposure to US golf comes from reading what GCA posters do, but this couldn't be further from the truth. Within 45 minutes of my childhood home are at least 6 golf "resorts." The closest of those to my hometown offers rates of $230 per person for three rounds, two nights lodging, two free breakfasts, and a $20 pro shop gift card. Any way you slice it, that's cheap. A quick glance at the websites of the other resorts suggests that their prices are comparable, if not lower. All prices include carts.
These resorts are all booked solid throughout the warmer months, and full of guests from out of state. The golf quality is somewhere between below-average and abysmal, but the "retail golfer" doesn't care. There are far more golfers in the US traveling to these and similar budget-friendly locations than there are traveling to places like Streamsong, Bandon, or Sand Valley. They just don't hang out on this website, and we don't discuss the budget-friendly locations here because the golf architecture sucks.