2020年起新的公約隻爭對中國，所以中國寄往美國的小包裹已經沒有啥優惠了

https://redstagfulfillment.com/universal-postal-union-treaty/

Impact On Small ECommerce Packages From China

On July 1, 2020, USPS raised the fees it charges for incoming parcels. International shippers, including from China, now have to pay $2.87 per package and $3.95 per kilogram (about 2.2 pounds). This is a huge increase in shipping costs on small parcels from China to the US. In the past, the cost to mail packages under 4.4 pounds (2 kilos) from China was less than the cost to ship the same package within the US. See below for more on the cheap postage that fueled China’s micro-eCommerce boom.

The bottom line is that the cost for shipping small packages from China to the US will be able double what it was in the past.