I'd imagine the vast majority of that was in the US, since while Amazon operates in many countries, in most it's only a pale shadow of the US juggernaut. For example, in Singapore it's nearly useless for anything except books, and even there local inventory is pretty sad.
Nowhere near as big as in the US though, and it's only active in the UK, the Netherlands, Germany, France, Spain, and Italy[1]. They have a total of 341 million people. In 2019, Amazon employed 600 000 people in the US, and only 115 000 in Europe[2].
For what it's worth, I'm in Portugal and have ordered from several amazon sites. Mostly it's from the Spanish one which gives free shipping on orders of 29€.
Because why setup a warehouse in Denmark when workers are half the price in Germany and shipping from Germany to Denmark is only marginally more expensive? I suspect the same is true for other countries like The Netherlands and Belgium.
