Purchasing and downloading Kindle books while in Soain

It's b/c your internet connection is outside the USA. Have you tried and used your phone cellular service as wifi hot spot and connect your kindle to that? I can't say would work but you could try. Another idea is to put the kindle app on your phone and "push" the books to that through the cellular service. I can't say would work but you could try.

A suggestion would be to use a VPN and set your location to the US. That, though, is an impractical solution in that it costs time and money (and a modicum of tech savvy) to pull off.

In related and perhaps a possible way, when we were in Curacao on the beach, my wife had forgotten her "beach read" book. I had my phone (airplane mode) and my Kindle, so I decided $10 (daily roaming fee) and the Kindle version of the book ($19 or so) was worth it to let her enjoy the day on the beach (between swimming & snorkeling).

Anyway, I couldn't buy through the Amazon app on my phone, but could buy through the Amazon.com website (using Safari browser), then paired my phone to my Kindle, and it downloaded immediately.
So, maybe, there is a way to use the US - Amazon.com - vs the Spain Amazon.es (or whatever) - to buy and then it downloads automatically. It worked in Curacao, so probably should in Spain.

Do you have a library card from home? If so, you may be able to go to the library website and download a free e-book for your kindle.

How are you trying to buy the books? Directly from the Kindle, through the apps? from their websites?

If you are using the app, that could be the problem. Amazon can't sell books through the Kindle app. Have you tried buying them directly from the Kindle? If not, how about the website?

Additionally, I have found that some hotel wifi systems are password protected and the Kindle itself is unable to connect to that network. It's even happened in the US. If that happens, then you will have to sideload the books.

A suggestion would be to use a VPN and set your location to the US. That, though, is an impractical solution in that it costs time and money (and a modicum of tech savvy) to pull off.

Google One offers a free VPN and you only need to pay $1.99 a month for 100GB of extra storage. Very easy to install. https://one.google.com/about/plans

FWIW, I was just in England and had no problem downloading eBooks from Amazon on my Kindle and using the hotel wifi. But I did use a VPN I received from Google One (see post above).

That said, last year in Scotland and the previous year in Germany, I was able to download books without a VPN. You might try changing locations. Sometimes I have not been able to use wifi on a Kindle when I was on a train or plane. But I've never had a problem with hotel wifi.

It would be helpful,, also, if you could give more details. For example, are you able to log in to your Amazon account, but then can't download the book? Do you get an error message?

I wanted to do that in New Zealand for books I thought I had already downloaded to my kindle. As someone else said, I put the app on my phone and downloaded the books from the website to my phone.