This is not just Amazon. There are a ****load of Chinese sellers on eBay selling all sorts of items at low or zero shipping cost to the buyer. I have purchased quite a few of such items myself, but I prefer buying from US sellers if they can get reasonably close on total cost (say, 20-30% more), and some do. Problem is, sometimes the item is ONLY available from a Chinese seller.* Other times the US sellers are 2x (or more) the item cost before one even gets to the shipping cost.
*Ok, so I buy some relatively uncommon items... :-)
Oddly enough (given my eBay “history”), in terms of $$ I’d say well under 5% of what I buy on Amazon comes from Chinese sellers. Last year, I don’t think anything I bought from Amazon shipped to me from China.
It's not just the USPS, while the USPS entered into a sweet heart deal for the Chinese and amazon. The cost of overnight shipping and 2nd shipping has gone way up for the individual. I'm guessing FedEx and UPS cut sweet heart deals with the big overnight shippers. Now the individual essentially pays a tax every time they have to ship something overnight just so FedEx/UPS can offer a discount to he Amazons of the world