But lets see the Positive side: Now the Nazis wont have to burn thousands of books, saving tons of co2 in their Plan to take over the world with propaganda. So, yay for the envoirment I guess
A hosting provider always has the ability to change what's on their infrastructure. The Kindle store is no different.
As it happens, they've been doing this for years. For example, the price you set as an author is not fixed nor is how it turns up on the page or how and when it's promoted.
The standard ebook format is essentially a zipped up series of text files.
Source: I sell my "Foundations of Amateur Radio" ebooks on the Kindle store
The bigger question is do they care. At worst they get a slap on the wrist by the US government. At best they get to control the narrative and have books like having history books on their platform talk about how the the Allies first striked Nazi Germany because they were lifting the country out of economic crisis and making the world a better place.
I doubt they'll care or listen if EU says stop since they'll just find a way around whatever they have planned to try and stop revisionist ideology from taking hold.