European here, not so young (50).
I have yet to come across somebody using an amazon echo, amazon button or even routinely talking to the voice assistant on their phone (I have seen people try the function and then abandon it). So anecdotical evidence would imply that these devices are a lot less popular in Europe or in my age class than in the USA.
I don’t know whether it is true or, if true, what the reason would be. Language barrier may be part of the reason. These devices work well in French or German or Spanish, etc… but the people I know tend to need French, German, Spanish, etc… AND English and that confuses these assistants.
Another reason could be that people do not order online as much as in the USA (is that true?).
Another reason could be that the services that these assistants offer are pretty much US-centric and not at all adapted to the local habits. They suppose that you will move by car, that all restaurants serve standard foods and belong to a chain, that customers are loyal to a single brand, etc… All these is a little strange to me.
Talking about me: I have a smartphone with an assistant, as they all have now. I tried to use it, found out that typing text or simply taping an app to open it was easier. I deactivated it at some point. I had to reactivate it to connect the phone to my car so that I can use it as a GPS, but I don’t think I have ever used it once since.
So I am really puzzled. I look at these devices and they appear to me like a subscription service that will lock you to a single vendor, for example Amazon for Alexa. I don’t see the point of paying a subscription (Amazon prime, for example) and then further subscriptions for music, videos, books, whatever and on top of that pay for a device that will only allow me to spend more money at Amazon. I have an Amazon account, no subscription service at amazon and when I need a book, I simply fire the old browser and order it. When I need groceries, I walk or drive to the growcer. The evolution of retail in the USA completely baffles me.