That doesn’t do buyers any good though does it? A few people breeding for themselves does not an industry make. And I’m also not sure that breeding imported mares to Chacco Blue or other EU based studs really counts as American breeding which is what I see people doing.
I’m sure there are some US bred 5* SJers but I can’t think of one off the top of my head. I had a US born and bred mare that threw two 1.45m horses by US studs back in the 90s. She only had 3 foals total and as a percentage of offspring I jokingly say she is the most successful US show jumping broodmare I’ve encountered, lol.
I do see lots of top event prospects and some really nice dressage horses at the young horse shows every year in the US. And super all rounder types, with excellent temperaments, often out of homebred stallions- those people know their audience. I don’t see the 1.3m+ types very often. I can go home to Ireland and it’s super easy to find those for reasonable prices too, even though SJ is not the main focus of most programs there are still enough doing it.