Please excuse me when I say, doesn't the answer to this seem incredibly obvious? Those two countries have vastly different land masses. In the US, we have so much more space that it never occurred to anyone that we'd fill it up with garbage. Garbage tips are one of the oldest human social creations. To this day, we learn most about ancient cultures from their rubbish heaps.

In Japan, with significantly less space, they have to be more efficient and effective at recycling, reusing and disposing of garbage.

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