Exactly. I don't understand why this isn't acknowledged more.
Banning plastic bags in the US does absolutely nothing for the plastic bags clogging waterways in Asia.
Sometimes people think plastic recycling in the US is shipped to Asia where it ends up in waterways but that's not a thing either. It might get buried in a landfill there rather than recycled, but compressed pallets of plastic recycling aren't getting dumped into rivers. That's not a thing. The bags aren't flying away in the wind or something either. All the plastic clogging rivers -- that's all local consumer littering.
I was under the impression that Americans landfilled their garbage. I don't doubt that waste export is a thing, but is it really that large a proportion?
The US is the only country in the developed world that hasn't ratified the Basel Convention [0] and the US exports close to a billion tons of plastic waste to other countries per year [1]. The trash you see building up in third world countries is in large part from the United States, not from those countries themselves.