You're probably not paying Amazon (US) directly, but instead their European subsidiary. Amazon (EU) is the importer buying services from Amazon (US) for a fee.

You're probably not paying Amazon (US) directly, but instead their European subsidiary. Amazon (EU) is the importer buying services from Amazon (US) for a fee. If that fee gets taxed, Amazon (US) could simply decide to charge nothing (or only a symbolic amount) until the trade spat blows over. In the case where a European customer uses resources (and causes costs) in the US, there's a risk of losing money if the "tariff" never goes away, so they would likely have to raise prices for that use case to account for the risk. If a European customer only causes costs in Europe, that risk is nil, so there wouldn't be a need to raise prices, but Amazon could decide that it's a good excuse to do so anyway.