There are plenty of Dutch online retailers (e.g. bol.com and coolblue.nl) but their prices are significantly higher (even factoring the slight difference in VAT). Considering we're supposed to be in a "single market", I've never been able to figure out why that is.
I only know about it from those people because they order so much on amazon.
They may be using amazon.de, but so are most central euro countries.
In Denmark, people generally either buy from .de or .co.uk.
Certainly people order less from amazon than in the states, but the presence is still pretty huge.
I live in Vienna, and I order a few orders from amazon every day. Last year I had over 600 amazon.de orders. Generally I try to order only Prime stuff.
The vast majority of orders (over 90%) come from Salzburg, Austria, although in a few occasions I even had same day shipping, those came from somewhere even closer.
The location printed on the label is the place they hand over the package (trucked from somewhere). I'm a bit surprised they seem to do that in such a volume in Salzburg. Previously they mostly used Allhaming (usually called Linz on packages).
For example, most my packages in Germany are labelled "Radefeld - Direct" but they originate from Poland or the Czech Republic, not the Amazon logistics center near that.
They also print a return address on the labels which is often another place distinct from outbound delivery (mostly Graben for me). Amazon uses multiple locations to accept packages and forward them to their warehouses.
I don't know anything about their same-day logistics though. It's the first time I hear that for Austrian addresses and no mention on their homepage, too.