First: I specified that I was providing them no less than three separate data points: location, language, shipping address. I wouldn't expect some tiny spanish

First: I specified that I was providing them no less than three separate data points: location, language, shipping address. I wouldn't expect some tiny spanish company to do this. However, with a global giant like Amazon I do. Especially when they have already solved the hard part - the logistics around international shipment and payments. The sensible thing for amazon.es to do when they detect a customer who is probably not from Spain (based in e.g. IP-based geolocation) would be top show some dismissable banner at the top of the page saying "We see you are visiting from Sweden. Would you like to read the core part of the site in English? <YES> <NO>")