Maybe we have more industrial plastic waste than Japan? My experiences in Japan are that they use many times more plastic packaging on products than we jse in the US. I find this data extremely hard to believe.
If I had to guess, it’s probably we (as in the US) consumes more. One takeout meal for my family is probably more plastic in weight than your grocery runs. My plastic foldable table is probably your annual amount. While it seems wasteful, plastic bags are very minimal compared to other items.
Although I agree that Japan uses lots of plastic everywhere, I can see how the sheer size of stuff in the US can easily offset for that. The average American man weighs 50% more than the average Japanese man (200 lbs vs. 135). The average househould trash container in the US is the size of a garbage truck in Japan (being dramatic with this one, but less than you'd think).
The trash cans I have seen in Japan are roughly the same size as the ones I see in the US. The garbage trucks are smaller (to fit on smaller roads).... but they have a lot more of them!
Go to Costco in Texas and watch the literal pallets of bottled water the people cart into their trucks. They make up for entire Japanese towns probably.
People in the US go through a lot of individually bottled water bought in large quantities--including in many many areas where the tap water is perfectly fine.
On the other hand there are vending machines for various drinks (not all in plastic admittedly) on almost every other Japanese street corner. So I'm not sure how it averages out.