The number of rivers does not really reflect the amount of contributing countries. For example the Nile passes through almost a dozen, the Niger through five and the Indus through three.

Yangtze --- China [1]

Indus --- China, India [2], Pakistan [3]

Yellow --- China

Hai He --- China

Ganges --- India, Bangladesh [4]

Pearl --- China, Tiny bit in Vietnam [5]

Amur --- China, Russia [6]

Mekong --- China, Myanmar [7], Laos [8], Thailand [9], Cambodia [10], Vietnam [11]

Nile --- Egypt [12], Sudan [13], South Sudan [14], Ethiopia [15], Uganda [16], Congo [17], Kenya [18], Tanzania [19], Rwanda [20], Burundi [21]

Niger --- Benin [22], Guinea [23], Mali [24], Niger [25], Nigeria [26]

So 26 countries, with China clearly the worst.

However the majority of the plastic coming out of these countries is because of goods destined for western countries. Import tax based on Oceanic plastic emissions, with money used to clean up oceans, is the solution. This funds ocean cleanup, encourages better disposal, and puts the cost on the person driving it (the consumer)

Like CO2, plastic in the ocean is an externality that the world pays for, but doesn't benefit from.

> However the majority of the plastic coming out of these countries is because of goods destined for western countries.

Citation needed.

This is an anecdote but almost every small plastic thing I can buy in a Walmart here in the States was manufactured in China

If you throw away the plastic in North America how does it get into Chinese rivers?