The US has a mature and highly diversified drone industry with excellent tech. It just isn't targeted at consumers, which is the market segment where DJI plays.
DJI does own the consumer segment, but they're also still usually the go-to brand for US commercial purposes as well. Their software and hardware reliability is leaps and bounds better than anything else on the market until you start getting into defense contractor territory.
Apparently even when used to maim, mutilate and murder other people, DJI is superior.