Im not surprised. We have pretty good waste management systems. Almost all of our trash ends up in landfills where it is compacted and covered each day. This prevents it from get into the ocean. However, many 3rd world countries have open dump sites instead of landfills. This allows the waste to wash into rivers and deposit into the ocean. Here is a video showing the magnitude of these open dump sites in some of these countries. From this it is easy to see just how much trash can wash into the ocean.

https://youtu.be/KHiHBuubsDE